b
c
c
c
b
c
c
b
b
c
b
b
b
c
b
b
b
c
c
b
b
b
b
c
c
b
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c