f
a
f
b
x
f
b
f
a
x
f
b
f
c
x
f
c
f
b
x
f
c
f
a
x
f
a
f
c
x
2.2
f
b
f
c
x
f
b
x
f
a
f
b
x
f
a
x
f
a
f
b
x
f
b
f
a
x
f
c
f
a
x
f
a
f
c
x
f
b
f
c
x
f
c
f
b
x
f
c
f
a
x
f
c
x
true
f
c
f
a
x
f
c
x
f
b
f
c
x
f
c
f
b
x
f
c
f
a
x
f
a
f
c
x
f
a
f
b
x
f
a
x
f
a
f
b
x
f
b
f
a
x
f
b
f
c
x
f
b
x
true
a
0
1
b
0
1
c
0
1
f
2
2
20163
f
2
1
2
0
f
a
f
b
x
f
b
f
a
x
f
c
f
a
x
f
a
f
c
x
f
b
f
c
x
f
c
f
b
x
f
a
f
b
x
f
b
f
a
x
f
c
f
a
x
f
a
f
c
x
f
b
f
c
x
f
c
f
b
x
f
a
f
b
x
f
b
f
a
x
f
c
f
a
x
f
a
f
c
x
f
b
f
c
x
f
c
f
b
x
true
Failed!
NaTT
certifiable-1.6