#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <list>
#include <iterator>
#include <cassert>
#include <numeric>
#include <functional>
#include <ctime>
#include <bitset>
#pragma warning(disable:4996) 

//#define ATCODER
#ifdef ATCODER
#include <atcoder/all>
#endif

typedef long long ll;
typedef unsigned long long ull;
#define LINF  9223300000000000000
#define LINF2 1223300000000000000
#define LINF3 1000000000000
#define INF 2140000000
//const long long MOD = 1000000007;
const long long MOD = 998244353;

using namespace std;
#ifdef ATCODER
using namespace atcoder;
#endif

char str[1000005];

void solve()
{
    scanf("%s", str);
    int n = strlen(str);

    set<char> z;
    for (int i = 0; i < n; i++) {
        z.insert(str[i]);
    }
    if (z.size() == 1) {
        printf("%d\n", n%2? -1: 0); return;
    }
    int bad = 0;
    for (int i = 0; i < n; i++) {
        int j = n - 1 - i;
        if (str[i] != str[j]) {
            bad = 1;
            break;
        }
    }
    if (bad==0) {
        if (n - 2 <= 1) {
            printf("%d\n", n % 2 ? -1 : 0);
        }
        else {
            printf("%d\n", n - 2);
        }
    }
    else {
        printf("%d\n", n);
    }

    return;
}

int main()
{
#if 1
    solve();
#else
    int T, t;
    scanf("%d", &T);
    for (t = 0; t < T; t++) {
        //printf("Case #%d: ", t + 1);
        solve();
    }
#endif
    return 0;
}