fib N sel N fib1 s 0 s 0 fib1 X Y cons X n__fib1 Y add X Y add 0 X X add s X Y s add X Y sel 0 cons X XS X sel s N cons X XS sel N activate XS fib1 X1 X2 n__fib1 X1 X2 activate n__fib1 X1 X2 fib1 X1 X2 activate X X 2.2 sel s N cons X XS sel N activate XS activate n__fib1 X1 X2 fib1 X1 X2 add s X Y add X Y fib N fib1 s 0 s 0 sel s N cons X XS activate XS fib1 X Y add X Y fib N sel N fib1 s 0 s 0 true fib N sel N fib1 s 0 s 0 false fib N fib1 s 0 s 0 false sel s N cons X XS sel N activate XS true s 1 1 1 activate 1 1 activate 1 0 fib1 2 0 n__fib1 2 2 3 fib1 2 1 2 2 fib 1 0 0 0 40651 sel 2 1 0 sel 2 0 cons 2 1 3 add 2 0 add 2 1 1 fib 1 0 sel s N cons X XS activate XS false activate n__fib1 X1 X2 fib1 X1 X2 false fib1 X Y add X Y false add s X Y add X Y true s 1 1 1 activate 1 1 activate 1 0 fib1 2 0 n__fib1 2 2 3 fib1 2 1 2 2 fib 1 0 0 0 40651 sel 2 0 sel 2 0 cons 2 1 3 add 2 1 0 add 2 1 1 fib 1 0 NaTT certifiable-1.6