The Pair of Characters

Max Reward: 100

There are N characters in an array A. All the characters occur only once except one that ocurs twice. Your task is to find out that character that occurs twice. All characters will be lowercase.

Input Format

A string that contains N characters each separated by a single space.

Output Format

The output expected is the character that occurs twice.

Sample Inputs

a b c d d e f
b b
a j h d f s e r s

Sample Outputs

d
b
s


Memory Limit

512M