if
true
X
Y
X
if
false
X
Y
Y
lteq
s
M
o
false
lteq
o
M
true
lteq
s
M
s
K
lteq
M
K
from
M
nil
nil
from
M
cons
H
Z
if
lteq
M
H
cons
H
Z
from
M
Z
chain
F
nil
nil
chain
F
cons
H
Z
cons
F
H
chain
F
from
F
H
Z
incch
X
chain
x
N
s
x
X
X
list
Y
list
Z
list
M
N
K
N
H
N
F
N
N
o
N
s
N
N
true
B
false
B
nil
list
cons
N
list
list
if
B
list
list
list
lteq
N
N
B
from
N
list
list
chain
N
N
list
list
incch
list
list
FULL
.