a
x1
b
b
x1
c
b
x1
d
x1
e
b
x1
c
c
x1
d
b
x1
b
f
x1
f
x1
a
e
x1
c
x1
x1
a
a
x1
f
x1
2.2
a
a
x1
f
x1
e
b
x1
c
x1
d
b
x1
f
x1
e
b
x1
c
c
x1
f
x1
a
e
x1
c
b
x1
d
x1
f
x1
e
x1
true
f
x1
e
x1
c
b
x1
d
x1
f
x1
a
e
x1
e
b
x1
c
x1
e
b
x1
c
c
x1
d
b
x1
f
x1
a
a
x1
f
x1
true
Failed!
NaTT
certifiable-1.6