top
sent
x
top
check
rest
x
rest
nil
sent
nil
rest
cons
x
y
sent
y
check
sent
x
sent
check
x
check
rest
x
rest
check
x
check
cons
x
y
cons
check
x
y
check
cons
x
y
cons
x
check
y
check
cons
x
y
cons
x
y
2.2
check
cons
x
y
check
y
top
sent
x
check
rest
x
top
sent
x
rest
x
top
sent
x
top
check
rest
x
check
rest
x
rest
check
x
check
cons
x
y
check
x
check
sent
x
check
x
check
rest
x
check
x
true
top
sent
x
top
check
rest
x
true
Failed!
NaTT
certifiable-1.6