#include<algorithm>
#include<iostream>
#include<vector>
#include<map>
#include<cassert>
#include<set>
#include<queue>
using namespace std;
using ll = long long;

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    string s;
    cin>>s;
    auto t = s;
    reverse(t.begin(),t.end());
    if(s!=t){
        cout<<s.size()<<endl;
        return 0;
    }
    sort(t.begin(),t.end());
    t.erase(unique(t.begin(),t.end()),t.end());
    if(t.size()==1){
        int n = s.size();
        if(n%2==0) cout<<0<<endl;
        else cout<<-1<<endl;
    }else{
        int n = s.size();
        if(n==3){
            cout<<-1<<endl;
            return 0;
        }
        cout<<n-2<<endl;
    }
}