Problem Description

Given a string containing only lowercase letters, please find the first character that appears only once. If there is none, output no.

Input Format

A string with a length less than $1100$.

Output Format

Output the first character that appears only once. If there is none, output no.

Sample Input and Output

Sample Input #1

abcabd

Sample Output #1

c

Sample Input #2

aabbcc

Sample Output #2

no

见题面 Input 部分

见题面 Output 部分