#include <bits/stdc++.h>

int main() {
  using namespace std;
  cin.tie(nullptr)->sync_with_stdio(false);
  string s;
  cin >> s;
  int n = size(s);
  if (count(begin(s), end(s), s[0]) == n) {
    cout << (n & 1 ? -1 : 0) << '\n';
    exit(0);
  }
  if (s != string(rbegin(s), rend(s))) {
    cout << n << '\n';
    exit(0);
  }
  if (n == 3) {
    cout << "-1\n";
    exit(0);
  }
  cout << n - 2 << '\n';
}