a
a
x1
b
b
b
x1
b
b
b
b
b
x1
a
a
a
x1
2.2
b
b
b
b
b
x1
a
a
x1
a
a
x1
b
x1
a
a
x1
b
b
x1
b
b
b
b
b
x1
a
x1
b
b
b
b
b
x1
a
a
a
x1
a
a
x1
b
b
b
x1
true
a
a
x1
b
b
b
x1
b
b
b
b
b
x1
a
a
a
x1
b
b
b
b
b
x1
a
x1
a
a
x1
b
x1
a
a
x1
b
b
x1
b
b
b
b
b
x1
a
a
x1
true
a
1
1
8
b
1
1
5
a
1
1
3
b
1
1
0
a
a
x1
b
b
b
x1
b
b
b
b
b
x1
a
a
a
x1
NaTT
certifiable-1.6