plus
x
y
plusIter
x
y
0
plusIter
x
y
z
ifPlus
le
x
z
x
y
z
ifPlus
true
x
y
z
y
ifPlus
false
x
y
z
plusIter
x
s
y
s
z
le
s
x
0
false
le
0
y
true
le
s
x
s
y
le
x
y
sum
xs
sumIter
xs
0
sumIter
xs
x
ifSum
isempty
xs
xs
x
plus
x
head
xs
ifSum
true
xs
x
y
x
ifSum
false
xs
x
y
sumIter
tail
xs
y
isempty
nil
true
isempty
cons
x
xs
false
head
nil
error
head
cons
x
xs
x
tail
nil
nil
tail
cons
x
xs
xs
a
b
a
c
2.2
plusIter
x
y
z
le
x
z
sumIter
xs
x
head
xs
le
s
x
s
y
le
x
y
sum
xs
sumIter
xs
0
ifPlus
false
x
y
z
plusIter
x
s
y
s
z
ifSum
false
xs
x
y
sumIter
tail
xs
y
plus
x
y
plusIter
x
y
0
sumIter
xs
x
plus
x
head
xs
sumIter
xs
x
ifSum
isempty
xs
xs
x
plus
x
head
xs
plusIter
x
y
z
ifPlus
le
x
z
x
y
z
ifSum
false
xs
x
y
tail
xs
sumIter
xs
x
isempty
xs
true
sum
xs
sumIter
xs
0
false
sumIter
xs
x
ifSum
isempty
xs
xs
x
plus
x
head
xs
ifSum
false
xs
x
y
sumIter
tail
xs
y
true
Failed!
NaTT
certifiable-1.6