#include <bits/stdc++.h>
using namespace std;
int main(){
  string S;
  cin >> S;
  string S2 = S;
  reverse(S2.begin(), S2.end());
  if (S != S2){
    cout << S.size() << endl;
  } else if (S.size() == 1){
    cout << -1 << endl;
  } else {
    S.pop_back();
    S.pop_back();
    S2.erase(S2.begin());
    S2.erase(S2.begin());
    if (S != S2){
      cout << S.size() << endl;
    } else {
      for (int i = 0; i < S.size(); i++){
        assert(S[i] == S[0]);
      }
      if (S.size() % 2 == 0){
        cout << 0 << endl;
      } else {
        cout << -1 << endl;
      }
    }
  }
}