a
a
x1
b
b
b
x1
a
x1
d
c
d
x1
b
b
x1
c
c
c
x1
c
c
x1
d
d
d
x1
c
d
d
x1
a
x1
2.2
c
d
d
x1
a
x1
a
a
x1
b
b
b
x1
a
a
x1
b
b
x1
b
b
x1
c
x1
b
b
x1
c
c
c
x1
a
x1
c
d
x1
a
a
x1
b
x1
b
b
x1
c
c
x1
true
b
b
x1
c
c
x1
a
a
x1
b
x1
a
x1
c
d
x1
b
b
x1
c
c
c
x1
a
a
x1
b
b
b
x1
b
b
x1
c
x1
a
a
x1
b
b
x1
c
d
d
x1
a
x1
true
a
1
1
42
d
1
1
12
b
1
1
27
c
1
1
18
c
1
1
0
a
1
1
23
b
1
1
10
c
c
x1
d
d
d
x1
a
a
x1
b
b
b
x1
b
b
x1
c
c
c
x1
c
d
d
x1
a
x1
a
x1
d
c
d
x1
NaTT
certifiable-1.6