a
a
b
b
x
b
b
b
a
a
a
x
a
c
x
c
a
x
c
b
x
b
c
x
dup
A'
a
b
b
x
collapse
A'
a
x
A'
a
x
collapse
x
y
dup
x
collapse
x
y
dup
y
2.2
a
c
x
a
x
a
a
b
b
x
a
a
a
x
dup
A'
a
b
b
x
collapse
A'
a
x
A'
a
x
dup
A'
a
b
b
x
a
x
a
a
b
b
x
a
a
x
dup
A'
a
b
b
x
a
x
c
b
x
c
x
collapse
x
y
dup
y
a
c
x
c
a
x
a
a
b
b
x
a
x
collapse
x
y
dup
x
true
collapse
x
y
dup
x
collapse
x
y
dup
y
dup
A'
a
b
b
x
collapse
A'
a
x
A'
a
x
true
Failed!
NaTT
certifiable-1.6