le
0
x
true
le
s
x
0
false
le
s
x
s
y
le
x
y
app
nil
x
x
app
cons
x
xs
ys
cons
x
app
xs
ys
split
x
nil
pair
nil
nil
qsort
nil
nil
split
x
cons
y
ys
pair
xs
cons
y
zs
split
x
ys
pair
xs
zs
le
x
y
true
split
x
cons
y
ys
pair
cons
y
xs
zs
split
x
ys
pair
xs
zs
le
x
y
false
qsort
cons
x
xs
app
qsort
ys
cons
x
qsort
zs
split
x
xs
pair
ys
zs
le
2
0
0
true
0
s
1
false
0
app
2
nil
0
cons
2
split
2
pair
2
qsort
1
ORIENTED
FULL