#include <bits/stdc++.h>
using namespace std;
 
#define endl '\n'
 
 
int main() 
{
    // Simple is BEAST
 
	string s;
	cin >> s;
 
	int n = s.size();
	map<char, int>mp;
	for(auto c : s)
		mp[c]++;
 
	int i = 0, j = n-1;
	while(i < j){
 
		if(mp[s[i]] > 1)mp[s[i]]--, i++;
		else if(mp[s[j]] > 1)mp[s[j]]--, j--;
		else if(mp[s[i]] == 1 and mp[s[j]] == 1)break;
 
	}
 
	cout << j-i+1 << endl;
 
 
    return 0;
}