Missing Letter

You are given an integer $N$ and a letterbox. The box

contains all letters, except one, from a to the $N+1^{th}$

alphabet. Your task is to write a program that can

find the missing letter.

Input

The first line of input contains an integer $N,$

representing the size of the array $ar.$

The second line of input contains $N$ space$-$separated

letters, representing the array of elements as unique

letters in the alphabet.

Output

Print the missing letter.

Constraints

$a$

Example #$1$

Input