fst 0 Z nil fst s X cons Y Z cons Y n__fst activate X activate Z from X cons X n__from s X add 0 X X add s X Y s n__add activate X Y len nil 0 len cons X Z s n__len activate Z fst X1 X2 n__fst X1 X2 from X n__from X add X1 X2 n__add X1 X2 len X n__len X activate n__fst X1 X2 fst X1 X2 activate n__from X from X activate n__add X1 X2 add X1 X2 activate n__len X len X activate X X 2.2 fst s X cons Y Z activate Z len cons X Z activate Z add s X Y activate X activate n__add X1 X2 add X1 X2 activate n__from X from X fst s X cons Y Z activate X activate n__len X len X activate n__fst X1 X2 fst X1 X2 true activate n__fst X1 X2 fst X1 X2 activate n__len X len X fst s X cons Y Z activate X len cons X Z activate Z activate n__add X1 X2 add X1 X2 add s X Y activate X fst s X cons Y Z activate Z true len 1 1 2941 s 1 1 1 activate 1 0 n__from 1 0 fst 2 0 activate 1 1 0 n__add 2 1 1 fst 2 1 2 2437 0 0 0 from 1 0 nil 0 0 n__len 1 1 2942 n__fst 2 1 2 2438 from 1 0 cons 2 2 5915 add 2 1 0 add 2 0 len 1 0 activate n__from X from X false NaTT certifiable-1.6