a
b
a
x1
b
a
x1
b
b
b
x1
b
a
b
x1
a
a
x1
b
b
b
x1
2.2
b
b
b
x1
a
b
x1
a
a
x1
b
x1
a
a
x1
b
b
b
x1
b
b
b
x1
b
a
b
x1
a
a
x1
b
b
x1
true
a
a
x1
b
b
x1
b
b
b
x1
b
a
b
x1
a
a
x1
b
b
b
x1
a
a
x1
b
x1
b
b
b
x1
a
b
x1
true
a
1
3
b
1
1
a
1
1
0
b
1
2
b
b
b
x1
b
a
b
x1
b
b
b
x1
b
a
b
x1
b
b
b
x1
b
a
b
x1
true
2
1
a
1
1
1
1
0
1
5
1
b
1
0
0
1
1
1
1
2
a
1
0
0
b
1
0
0
1
0
1
0
0
a
b
a
x1
b
a
x1
a
a
x1
b
b
b
x1
b
b
b
x1
b
a
b
x1
NaTT
certifiable-1.6