#include<iostream>
#include<string>
using namespace std;
#define rep(i,s,n) for (int i=s;i<n;i++)
int main(){

  string S;cin>>S;
  int n=S.length();
  int bef=S[0];
  bool kaibun=true,same=true;
  rep(i,0,n/2){
    if(S[i]!=S[n-1-i]){
      kaibun=same=false;
      break;
    }
    if(bef!=S[i] || bef!=S[n-1-i]){
      same=false;
    }
    bef=S[i];
  }
  if((n%2)&&bef!=S[n/2])same=false;
  if(same){
    if(n>1)
    cout<<0;
    else
    cout<<-1;
  }else if(kaibun){
    if(n>3)
    cout<<n-2;
    else
    cout<<-1;
  }else{
    cout<<n;
  }cout<<endl;
}