[Link] https://www.acmicpc.net/problem/15927
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#include <algorithm>
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <cstring>
#include <stack>
#include <cmath>
// #include <bits/stdc++.h>
using namespace std;
#define for0(i, n) for(int i = 0; i < n; i++)
#define for1(i, n) for(int i = 1; i < n; i++)
#define fori(s, e) for(int i = s; i < e; i++)
#define ll long long
#define endl "\n"
#define nulls '\0'
#define dkdk " "
const int MAX = 5e5 + 1;
const int INF = 987654321;
string s;
int solve() {
int l = 0, r = s.size() - 1;
bool all_same = true, is_pal = true;
while(l <= r) {
if(s[l] != s[r]) { all_same = false; is_pal = false; break; }
if(l && s[l-1] != s[l]) all_same = false;
l++; r--;
}
return is_pal ? (all_same ? -1 : s.size() - 1) : s.size();
}
int main(int argc, char *argv[]) {
cin >> s;
cout << solve();
return 0;
}