#include <bits/stdc++.h>
using namespace std;

int main(){
	string s;
	cin>>s;
	for(int i = 0;i < s.size();i++){
		for(int j = i+1;j < s.size();j++){
			if(s[i] == s[j]){
				cout<<s[i];
				return 0;
			}
		}
	} 
	cout<<s.size();
	return 0;
}

/**************************************************************
	Problem: 1978
	User: admin
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2076 kb
****************************************************************/