#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<bitset>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<deque>
#include<list>
#include<iomanip>
#include<cmath>
#include<cstring>
#include<functional>
#include<cstdio>
#include<cstdlib>
#include<numeric>
#include<ctime>
//#include<atcoder/all>
using namespace std;
//using namespace atcoder;

#define repr(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repr(i, 0, n)
#define INF 2e9
//#define MOD 1000000007
#define MOD 998244353
#define LINF (long long)4e18
#define jck 3.141592
#define PI acos(-1.0)

const double EPS = 1e-10;

using ll = long long;
using Pi = pair<int,int>;
using Pl = pair<ll,ll>;
//using mint = modint998244353;

int dh[] = {1,0,-1,0};
int dw[] = {0,1,0,-1};

int main(){
    string s; cin >> s;
    int n = s.size();
    set<char> st;
    rep(i,n) st.insert(s[i]);
    if(st.size() == 1){
        if(n%2 == 0) cout << 0 << endl;
        else cout << -1 << endl;
        return 0;
    }
    bool ok = true;
    rep(i,n){
        if(s[i] != s[n-i-1]) ok = false;
    }
    if(ok){
        if(n == 3) cout << -1 << endl;
        else cout << n-2 <<endl;
    }
    else cout << n << endl;
}