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