#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

bool judge(string s){
    int n = s.size();
    for(int i = 0; i < n; i++){
        if(s[i] != s[n-i-1]) return false;
    }
    return true;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    set<char> st;
    string s; cin >> s;
    if(s.size() <= 1){
        cout << -1 << endl;
        return 0;
    }
    for(char c: s) st.insert(c);
    if(st.size() == 1){
        if(s.size()%2 == 0) cout << 0 << endl;
        else cout << -1 << endl;
        return 0;
    }
    if(judge(s)){
        if(s.size() == 3) cout << -1 << endl;
        else cout << s.size()-2 << endl;
    }else{
        cout << s.size() << endl;
    }
}