a
b
a
x1
b
b
b
x1
b
a
b
x1
a
b
a
x1
2.2
b
a
b
x1
b
a
x1
a
b
a
x1
b
x1
a
b
a
x1
b
b
x1
b
a
b
x1
a
x1
b
a
b
x1
a
b
a
x1
a
b
a
x1
b
b
b
x1
true
a
b
a
x1
b
b
b
x1
b
a
b
x1
a
b
a
x1
b
a
b
x1
a
x1
a
b
a
x1
b
x1
a
b
a
x1
b
b
x1
b
a
b
x1
b
a
x1
true
a
1
1
7720
b
1
1
7720
a
1
1
0
b
1
1
0
b
a
b
x1
a
b
a
x1
a
b
a
x1
b
b
b
x1
a
b
a
x1
b
b
b
x1
b
a
b
x1
a
b
a
x1
a
b
a
x1
b
b
b
x1
b
a
b
x1
a
b
a
x1
true
Failed!
NaTT
certifiable-1.6