```cpp
#include<stdio.h>
#include<iostream>
#include<cmath>
#include<string>
using namespace std;
int main(){
	int a[128] = { 0 };//记录字符对应的ascii码出现次数
	string s;
	getline(cin, s);
	for (int i = 0; i <s.length(); i++) {
		int x=s[i];
		a[x]++;
	}
	for (int i = 0; i <128; i++) {
		if (a[i] == 1) {//要找的字符
			char ch=i;//转换为字符类型
			cout << ch;
			return 0;
		}
	}
	cout << "no";
		return 0;
}