sort
nil
nil
sort
cons
x
y
insert
x
sort
y
insert
x
nil
cons
x
nil
insert
x
cons
v
w
choose
x
cons
v
w
x
v
choose
x
cons
v
w
y
0
cons
x
cons
v
w
choose
x
cons
v
w
0
s
z
cons
v
insert
x
w
choose
x
cons
v
w
s
y
s
z
choose
x
cons
v
w
y
z
2.2
sort
cons
x
y
sort
y
insert
x
cons
v
w
choose
x
cons
v
w
x
v
choose
x
cons
v
w
0
s
z
insert
x
w
sort
cons
x
y
insert
x
sort
y
choose
x
cons
v
w
s
y
s
z
choose
x
cons
v
w
y
z
true
sort
cons
x
y
sort
y
true
insert
2
0
s
1
0
insert
2
0
choose
4
0
sort
1
1
0
0
0
0
nil
0
0
sort
1
0
choose
4
0
cons
2
2
1
sort
cons
x
y
insert
x
sort
y
false
choose
x
cons
v
w
s
y
s
z
choose
x
cons
v
w
y
z
choose
x
cons
v
w
0
s
z
insert
x
w
insert
x
cons
v
w
choose
x
cons
v
w
x
v
true
insert
2
1
2
1
s
1
1
insert
2
0
choose
4
1
2
0
sort
1
0
0
0
1
nil
0
0
sort
1
0
choose
4
0
cons
2
1
2
2
choose
x
cons
v
w
s
y
s
z
choose
x
cons
v
w
y
z
choose
x
cons
v
w
s
y
s
z
choose
x
cons
v
w
y
z
true
insert
2
1
s
1
1
1
insert
2
0
choose
4
4
0
sort
1
0
0
0
1
nil
0
0
sort
1
0
choose
4
0
cons
2
2
NaTT
certifiable-1.6