Score : $200$ points
Takahashi is practicing shiritori alone again today.
Shiritori is a game as follows:
In this game, he is practicing to announce as many words as possible in ten seconds.
You are given the number of words Takahashi announced, $N$, and the $i$-th word he announced, $W_i$, for each $i$. Determine if the rules of shiritori was observed, that is, every word announced by him satisfied the conditions.
Input is given from Standard Input in the following format:
$N$ $W_1$ $W_2$ $:$ $W_N$
If every word announced by Takahashi satisfied the conditions, print
Yes; otherwise, print
4 hoge english hoge enigma
hoge is announced multiple times, the rules of shiritori was not observed.
9 basic c cpp php python nadesico ocaml lua assembly
8 a aa aaa aaaa aaaaa aaaaaa aaa aaaaaaa
3 abc arc agc