a
a
x1
b
b
b
x1
b
b
x1
c
c
c
x1
c
c
c
c
x1
a
b
x1
2.2
b
b
x1
c
c
x1
a
a
x1
b
b
b
x1
a
a
x1
b
b
x1
c
c
c
c
x1
b
x1
b
b
x1
c
x1
b
b
x1
c
c
c
x1
a
a
x1
b
x1
c
c
c
c
x1
a
b
x1
true
c
c
c
c
x1
a
b
x1
a
a
x1
b
x1
b
b
x1
c
c
c
x1
b
b
x1
c
x1
a
a
x1
b
b
b
x1
c
c
c
c
x1
b
x1
a
a
x1
b
b
x1
b
b
x1
c
c
x1
true
a
1
1
23
b
1
1
15
c
1
1
10
c
1
1
0
a
1
1
14
b
1
1
6
a
a
x1
b
b
b
x1
c
c
c
c
x1
a
b
x1
b
b
x1
c
c
c
x1
NaTT
certifiable-1.6