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
top
1
sent
1
check
1
rest
1
nil
0
cons
2
FULL
./TRS/AProVE/Liveness6.2.trs