active fst 0 Z mark nil active fst s X cons Y Z mark cons Y fst X Z active from X mark cons X from s X active add 0 X mark X active add s X Y mark s add X Y active len nil mark 0 active len cons X Z mark s len Z active cons X1 X2 cons active X1 X2 active fst X1 X2 fst active X1 X2 active fst X1 X2 fst X1 active X2 active from X from active X active add X1 X2 add active X1 X2 active add X1 X2 add X1 active X2 active len X len active X cons mark X1 X2 mark cons X1 X2 fst mark X1 X2 mark fst X1 X2 fst X1 mark X2 mark fst X1 X2 from mark X mark from X add mark X1 X2 mark add X1 X2 add X1 mark X2 mark add X1 X2 len mark X mark len X proper 0 ok 0 proper s X s proper X proper nil ok nil proper cons X1 X2 cons proper X1 proper X2 proper fst X1 X2 fst proper X1 proper X2 proper from X from proper X proper add X1 X2 add proper X1 proper X2 proper len X len proper X s ok X ok s X cons ok X1 ok X2 ok cons X1 X2 fst ok X1 ok X2 ok fst X1 X2 from ok X ok from X add ok X1 ok X2 ok add X1 X2 len ok X ok len X top mark X top proper X top ok X top active X 2.2 active fst s X cons Y Z fst X Z proper fst X1 X2 proper X1 active fst X1 X2 active X2 proper add X1 X2 proper X2 top mark X proper X proper fst X1 X2 fst proper X1 proper X2 add mark X1 X2 add X1 X2 proper from X from proper X len mark X len X active cons X1 X2 active X1 fst mark X1 X2 fst X1 X2 proper from X proper X top ok X top active X from mark X from X fst ok X1 ok X2 fst X1 X2 active from X s X active from X active X active add X1 X2 active X2 active fst X1 X2 active X1 proper cons X1 X2 proper X2 proper cons X1 X2 proper X1 top mark X top proper X active from X from active X active add s X Y s add X Y proper s X s proper X from ok X from X active cons X1 X2 cons active X1 X2 active from X cons X from s X add X1 mark X2 add X1 X2 active len X active X top ok X active X fst X1 mark X2 fst X1 X2 active fst X1 X2 fst active X1 X2 proper add X1 X2 add proper X1 proper X2 len ok X len X proper fst X1 X2 proper X2 active fst X1 X2 fst X1 active X2 proper cons X1 X2 cons proper X1 proper X2 proper add X1 X2 proper X1 active len cons X Z len Z active add X1 X2 active X1 active add s X Y add X Y active len X len active X active len cons X Z s len Z add ok X1 ok X2 add X1 X2 s ok X s X active add X1 X2 add active X1 X2 proper len X len proper X active fst s X cons Y Z cons Y fst X Z cons mark X1 X2 cons X1 X2 active add X1 X2 add X1 active X2 proper s X proper X proper len X proper X active from X from s X cons ok X1 ok X2 cons X1 X2 true top mark X top proper X top ok X top active X true len 1 0 cons 2 0 s 1 11650 top 1 0 fst 2 1 2 43209 top 1 1 0 fst 2 0 proper 1 1 0 ok 1 1 0 0 0 5876 from 1 1 41055 s 1 0 nil 0 32018 mark 1 1 1 proper 1 0 from 1 0 active 1 1 0 cons 2 1 41054 active 1 0 add 2 0 add 2 1 2 12280 len 1 1 1 top ok X top active X from mark X mark from X active add 0 X mark X cons mark X1 X2 mark cons X1 X2 active cons X1 X2 cons active X1 X2 active fst 0 Z mark nil active from X mark cons X from s X fst mark X1 X2 mark fst X1 X2 len mark X mark len X proper fst X1 X2 fst proper X1 proper X2 add mark X1 X2 mark add X1 X2 fst ok X1 ok X2 ok fst X1 X2 fst X1 mark X2 mark fst X1 X2 proper from X from proper X add ok X1 ok X2 ok add X1 X2 proper 0 ok 0 proper add X1 X2 add proper X1 proper X2 active add s X Y mark s add X Y from ok X ok from X active fst X1 X2 fst X1 active X2 active len cons X Z mark s len Z add X1 mark X2 mark add X1 X2 proper cons X1 X2 cons proper X1 proper X2 s ok X ok s X active len X len active X cons ok X1 ok X2 ok cons X1 X2 active add X1 X2 add active X1 X2 proper s X s proper X proper nil ok nil active from X from active X active fst X1 X2 fst active X1 X2 active add X1 X2 add X1 active X2 active len nil mark 0 len ok X ok len X proper len X len proper X active fst s X cons Y Z mark cons Y fst X Z top ok X top active X true len 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 1 1 top 1 1 0 fst 2 0 proper 1 1 27377 ok 1 1 27377 0 0 1 from 1 1 1 s 1 0 nil 0 32018 mark 1 1 proper 1 0 from 1 0 active 1 1 1 cons 2 1 1 active 1 0 add 2 0 add 2 1 1 len 1 1 0 from mark X mark from X active add 0 X mark X cons mark X1 X2 mark cons X1 X2 active cons X1 X2 cons active X1 X2 active fst 0 Z mark nil active from X mark cons X from s X fst mark X1 X2 mark fst X1 X2 len mark X mark len X proper fst X1 X2 fst proper X1 proper X2 add mark X1 X2 mark add X1 X2 fst ok X1 ok X2 ok fst X1 X2 fst X1 mark X2 mark fst X1 X2 proper from X from proper X add ok X1 ok X2 ok add X1 X2 proper 0 ok 0 proper add X1 X2 add proper X1 proper X2 active add s X Y mark s add X Y from ok X ok from X active fst X1 X2 fst X1 active X2 active len cons X Z mark s len Z add X1 mark X2 mark add X1 X2 proper cons X1 X2 cons proper X1 proper X2 s ok X ok s X active len X len active X cons ok X1 ok X2 ok cons X1 X2 active add X1 X2 add active X1 X2 proper s X s proper X proper nil ok nil active from X from active X active fst X1 X2 fst active X1 X2 active add X1 X2 add X1 active X2 active len nil mark 0 len ok X ok len X proper len X len proper X active fst s X cons Y Z mark cons Y fst X Z top mark X proper X false top ok X active X false proper len X proper X proper s X proper X proper cons X1 X2 proper X1 proper cons X1 X2 proper X2 proper from X proper X proper add X1 X2 proper X1 proper fst X1 X2 proper X2 proper add X1 X2 proper X2 proper fst X1 X2 proper X1 true len 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 1 2 1 top 1 1 0 fst 2 0 proper 1 1 0 ok 1 1 0 0 1 from 1 1 11575 s 1 0 nil 0 1 mark 1 625 proper 1 1 0 from 1 0 active 1 1 21027 cons 2 1 2 1 active 1 0 add 2 0 add 2 1 2 1 len 1 1 1 from mark X mark from X active add 0 X mark X cons mark X1 X2 mark cons X1 X2 active cons X1 X2 cons active X1 X2 active fst 0 Z mark nil active from X mark cons X from s X fst mark X1 X2 mark fst X1 X2 len mark X mark len X proper fst X1 X2 fst proper X1 proper X2 add mark X1 X2 mark add X1 X2 fst ok X1 ok X2 ok fst X1 X2 fst X1 mark X2 mark fst X1 X2 proper from X from proper X add ok X1 ok X2 ok add X1 X2 proper 0 ok 0 proper add X1 X2 add proper X1 proper X2 active add s X Y mark s add X Y from ok X ok from X active fst X1 X2 fst X1 active X2 active len cons X Z mark s len Z add X1 mark X2 mark add X1 X2 proper cons X1 X2 cons proper X1 proper X2 s ok X ok s X active len X len active X cons ok X1 ok X2 ok cons X1 X2 active add X1 X2 add active X1 X2 proper s X s proper X proper nil ok nil active from X from active X active fst X1 X2 fst active X1 X2 active add X1 X2 add X1 active X2 active len nil mark 0 len ok X ok len X proper len X len proper X active fst s X cons Y Z mark cons Y fst X Z proper len X len proper X false proper s X s proper X false proper cons X1 X2 cons proper X1 proper X2 false proper add X1 X2 add proper X1 proper X2 false proper from X from proper X false proper fst X1 X2 fst proper X1 proper X2 false active fst X1 X2 active X1 active add X1 X2 active X2 active from X active X active add X1 X2 active X1 active cons X1 X2 active X1 active fst X1 X2 active X2 active len X active X true len 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 1 2 1 top 1 1 0 fst 2 0 proper 1 1 0 ok 1 1 0 0 1 from 1 1 11575 s 1 0 nil 0 1 mark 1 1 proper 1 0 from 1 0 active 1 1 1 cons 2 1 2 1 active 1 1 0 add 2 0 add 2 1 2 1 len 1 1 12063 from mark X mark from X active add 0 X mark X cons mark X1 X2 mark cons X1 X2 active cons X1 X2 cons active X1 X2 active fst 0 Z mark nil active from X mark cons X from s X fst mark X1 X2 mark fst X1 X2 len mark X mark len X proper fst X1 X2 fst proper X1 proper X2 add mark X1 X2 mark add X1 X2 fst ok X1 ok X2 ok fst X1 X2 fst X1 mark X2 mark fst X1 X2 proper from X from proper X add ok X1 ok X2 ok add X1 X2 proper 0 ok 0 proper add X1 X2 add proper X1 proper X2 active add s X Y mark s add X Y from ok X ok from X active fst X1 X2 fst X1 active X2 active len cons X Z mark s len Z add X1 mark X2 mark add X1 X2 proper cons X1 X2 cons proper X1 proper X2 s ok X ok s X active len X len active X cons ok X1 ok X2 ok cons X1 X2 active add X1 X2 add active X1 X2 proper s X s proper X proper nil ok nil active from X from active X active fst X1 X2 fst active X1 X2 active add X1 X2 add X1 active X2 active len nil mark 0 len ok X ok len X proper len X len proper X active fst s X cons Y Z mark cons Y fst X Z active fst s X cons Y Z cons Y fst X Z false active fst s X cons Y Z fst X Z false active add X1 X2 add X1 active X2 false active fst X1 X2 fst active X1 X2 false active from X from active X false active add X1 X2 add active X1 X2 false active len X len active X false active len cons X Z s len Z false active len cons X Z len Z false len mark X len X len ok X len X true len 1 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 1 1 top 1 1 0 fst 2 0 proper 1 1 1 ok 1 1 1 0 0 1 from 1 1 32570 s 1 0 nil 0 1 mark 1 1 0 proper 1 0 from 1 0 active 1 1 2 cons 2 2 1 active 1 0 add 2 0 add 2 2 44249 len 1 1 0 len mark X len X from mark X mark from X active add 0 X mark X cons mark X1 X2 mark cons X1 X2 active cons X1 X2 cons active X1 X2 active fst 0 Z mark nil active from X mark cons X from s X fst mark X1 X2 mark fst X1 X2 len mark X mark len X proper fst X1 X2 fst proper X1 proper X2 add mark X1 X2 mark add X1 X2 fst ok X1 ok X2 ok fst X1 X2 fst X1 mark X2 mark fst X1 X2 proper from X from proper X add ok X1 ok X2 ok add X1 X2 proper 0 ok 0 proper add X1 X2 add proper X1 proper X2 active add s X Y mark s add X Y from ok X ok from X active fst X1 X2 fst X1 active X2 active len cons X Z mark s len Z add X1 mark X2 mark add X1 X2 proper cons X1 X2 cons proper X1 proper X2 s ok X ok s X active len X len active X cons ok X1 ok X2 ok cons X1 X2 active add X1 X2 add active X1 X2 proper s X s proper X proper nil ok nil active from X from active X active fst X1 X2 fst active X1 X2 active add X1 X2 add X1 active X2 active len nil mark 0 len ok X ok len X proper len X len proper X active fst s X cons Y Z mark cons Y fst X Z len mark X len X true len 1 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 2 1 top 1 0 fst 2 0 proper 1 1 1 ok 1 1 1 0 0 1 from 1 1 1 s 1 0 nil 0 1 mark 1 1 1 proper 1 0 from 1 0 active 1 1 3 cons 2 2 1 active 1 0 add 2 0 add 2 2 1 len 1 1 0 from mark X mark from X active add 0 X mark X active fst 0 Z mark nil len mark X mark len X proper 0 ok 0 from ok X ok from X active len cons X Z mark s len Z s ok X ok s X proper nil ok nil active len nil mark 0 len ok X ok len X active fst X1 X2 fst X1 active X2 false fst ok X1 ok X2 fst X1 X2 fst mark X1 X2 fst X1 X2 fst X1 mark X2 fst X1 X2 true len 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 2 1 top 1 0 fst 2 1 0 proper 1 1 1 ok 1 1 1 0 0 1 from 1 1 1 s 1 0 nil 0 3 mark 1 1 1 proper 1 0 from 1 0 active 1 1 3 cons 2 2 1 active 1 0 add 2 0 add 2 2 1 len 1 1 0 fst X1 mark X2 fst X1 X2 from mark X mark from X active add 0 X mark X active fst 0 Z mark nil len mark X mark len X proper 0 ok 0 from ok X ok from X active len cons X Z mark s len Z s ok X ok s X proper nil ok nil active len nil mark 0 len ok X ok len X fst X1 mark X2 fst X1 X2 true len 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 2 1 top 1 0 fst 2 2 0 proper 1 1 1 ok 1 1 1 0 0 1 from 1 1 1 s 1 0 nil 0 1 mark 1 1 14756 proper 1 0 from 1 0 active 1 1 14758 cons 2 2 1 active 1 0 add 2 0 add 2 2 1 len 1 1 0 from mark X mark from X active add 0 X mark X active fst 0 Z mark nil len mark X mark len X proper 0 ok 0 from ok X ok from X active len cons X Z mark s len Z s ok X ok s X proper nil ok nil active len nil mark 0 len ok X ok len X active add s X Y s add X Y false active add s X Y add X Y false add X1 mark X2 add X1 X2 add ok X1 ok X2 add X1 X2 add mark X1 X2 add X1 X2 true len 1 0 cons 2 0 s 1 1 31675 top 1 0 fst 2 2 1 top 1 0 fst 2 0 proper 1 1 1 ok 1 1 1 0 0 1 from 1 1 1 s 1 0 nil 0 1 mark 1 1 1 proper 1 0 from 1 0 active 1 1 63039 cons 2 2 31363 active 1 0 add 2 1 2 0 add 2 2 1 len 1 1 0 from mark X mark from X active add 0 X mark X active fst 0 Z mark nil len mark X mark len X proper 0 ok 0 from ok X ok from X active len cons X Z mark s len Z s ok X ok s X proper nil ok nil active len nil mark 0 len ok X ok len X active from X cons X from s X false active from X from s X false from ok X from X from mark X from X true len 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 2 1 top 1 0 fst 2 0 proper 1 1 1 ok 1 1 1 0 0 1 from 1 1 1 s 1 0 nil 0 1 mark 1 1 1 proper 1 0 from 1 1 0 active 1 1 3 cons 2 2 1 active 1 0 add 2 0 add 2 2 1 len 1 1 0 from mark X mark from X active add 0 X mark X active fst 0 Z mark nil len mark X mark len X proper 0 ok 0 from ok X ok from X active len cons X Z mark s len Z s ok X ok s X proper nil ok nil active len nil mark 0 len ok X ok len X active from X s X false s ok X s X true len 1 0 cons 2 0 s 1 1 1 top 1 0 fst 2 2 1 top 1 0 fst 2 0 proper 1 1 1 ok 1 1 1 0 0 1 from 1 1 16898 s 1 1 0 nil 0 1 mark 1 1 1 proper 1 0 from 1 0 active 1 1 3 cons 2 2 1 active 1 0 add 2 0 add 2 2 1 len 1 1 0 from mark X mark from X active add 0 X mark X active fst 0 Z mark nil len mark X mark len X proper 0 ok 0 from ok X ok from X active len cons X Z mark s len Z s ok X ok s X proper nil ok nil active len nil mark 0 len ok X ok len X active cons X1 X2 cons active X1 X2 false cons ok X1 ok X2 cons X1 X2 cons mark X1 X2 cons X1 X2 true len 1 0 cons 2 1 0 s 1 1 1 top 1 0 fst 2 2 1 top 1 0 fst 2 0 proper 1 1 1 ok 1 1 1 0 0 1 from 1 1 1 s 1 0 nil 0 1 mark 1 1 1 proper 1 0 from 1 0 active 1 1 3 cons 2 2 1 active 1 0 add 2 0 add 2 2 1 len 1 1 0 from mark X mark from X active add 0 X mark X active fst 0 Z mark nil len mark X mark len X proper 0 ok 0 from ok X ok from X active len cons X Z mark s len Z s ok X ok s X proper nil ok nil active len nil mark 0 len ok X ok len X NaTT certifiable-1.6