#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using uint = unsigned;
using ull = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;


bool is_palindrome(const string &s, char c = '?'){
    auto n = s.length();
    for (int i = 0; i < (n+1)/2; ++i) {
        if(s[i] == c || s[n-i-1] == c) continue;
        if(s[i] != s[n-i-1]) return false;
    }
    return true;
}
int main() {
    string s;
    cin >> s;
    int same = 1;
    int n = s.size();
    for (int i = 0; i+1 < n; ++i) {
        if(s[i] != s[i+1]) same = 0;
    }
    if(same){
        puts(n%2 == 0 ? "0" : "-1");
        return 0;
    }else if(!is_palindrome(s)) {
        cout << n << "\n";
    }else if(n != 3) {
        cout << n-2 << "\n";
    }else {
        cout << -1 << "\n";
    }
    return 0;
}