#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll=long long;
using Graph=vector<vector<pair<int,int>>>;
#define MAX 100
#define MOD 998244353
#define INF 1000000000

int main(){
  string S;
  cin>>S;
  int N=S.size();
  for(int i=0;i<N/2;i++){
    if(S[i]!=S[N-1-i]){
      cout<<N<<endl;
      return 0;
    }
  }
  if(N==3){
    cout<<-1<<endl;
    return 0;
  }
  for(int i=1;i<N;i++){
    if(S[i]!=S[0]){
      cout<<N-2<<endl;
      return 0;
    }
  }
  if(N%2==1){
    cout<<-1<<endl;
  }else{
    cout<<0<<endl;
  }
}