#include "bits/stdc++.h" #define int long long using namespace std; using ll = long long; using P = pair; const ll INF = (1LL << 61); ll mod = 1000000007; signed main() { ios::sync_with_stdio(false); cin.tie(0); string S; cin >> S; int N = S.size(); if (N == 1) { cout << -1 << endl; return 0; } string T = S; reverse(T.begin(), T.end()); if (S != T) { cout << N << endl; return 0; } char c = S[0]; bool ok = true; for (int i = 0; i < N; i++)if (c != S[i])ok = false; if (ok) { cout << 0 << endl; } else { cout << N - 2 << endl; } return 0; }