F. Tilting Tiles
time limit per test
3 seconds
memory limit per test
1024 megabytes
input
standard input
output
standard output
Examples
Input
4 4
.r..
rgyb
.b..
.yr.

yrbr
..yr
...g
...b
Output
yes
Input
1 7
....x..

..x....
Output
no
Input
4 3
yr.
..b
ry.
b..

...
..b
.ry
byb
Output
no