309335: CF1663E. Are You Safe?

Seven boys and seven girls from Athens were brought before King Minos. The evil king laughed and said "I hope you enjoy your stay in Crete".

With a loud clang, the doors behind them shut, and darkness reigned. The terrified children huddled together. In the distance they heard a bellowing, unholy roar.

Bravely, they advanced forward, to their doom.

$n$ ($1 \le n \le 100$) — the dimensions of the labyrinth.

Each of the next $n$ lines contains a string of lowercase English letters of length $n$.

10
atzxcodera
mzhappyayc
mineodteri
trxesonaac
mtollexcxc
hjikeoutlc
eascripsni
rgvymnjcxm
onzazwswwg
geothermal

YES