a
b
x1
b
a
a
x1
b
x1
c
a
c
x1
a
a
x1
a
c
a
x1
2.2
a
a
x1
a
c
a
x1
a
b
x1
a
x1
a
b
x1
b
a
a
x1
b
x1
a
c
x1
a
b
x1
a
a
x1
true
a
b
x1
a
a
x1
a
b
x1
a
x1
true
a
1
1
0
b
1
1
1
c
1
0
a
1
1
0
b
1
0
a
b
x1
b
a
a
x1
a
a
x1
a
c
a
x1
b
x1
c
a
c
x1
a
b
x1
b
a
a
x1
false
b
x1
a
c
x1
false
a
a
x1
a
c
a
x1
false
NaTT
certifiable-1.6