a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
b b b b b b b b b b b b b b b b b b b b b b b b b b b b b
a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
b b b b b b b b b b b b b b b b b b b b b b b b b b b b b
a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
b b b b b b b b b b b b b b b b b b b b b b b b b b b b b
a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
b b b b b b b b b b b b b b b b b b b b b b b b b b b b b
a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
b b b b b b b b b b b b b b b b b b b b b b b b b b b b b
a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
b b b b b b b b b b b b b b b b b b b b b b b b b b b b b
a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
b b b b b b b b b b b b b b b b b b b b b b b b b b b b b
a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
b b b b b b b b b b b b b b b b b b b b b b b b b b b b b