#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

int main(){
  string S; cin >> S;
  string rS = S;
  reverse(S.begin(),S.end());
  if(S != rS){
    cout << S.size() << "\n";
    return 0;
  }
  if(S == string(S.size(),S[0])){
    if(S.size() % 2 == 0) cout << "0\n";
    else cout << "-1\n";
    return 0;
  }
  if(S.size() == 3){
    cout << "-1\n";
    return 0;
  }
  cout << (S.size() - 2) << "\n";
  return 0;
}