#include <bits/stdc++.h>

using namespace std;

#define int long long
#define ll long long
#define forn(i, n) for (ll i = 0; i < n; ++i)
#define forr(i, s, n) for (ll i = s; i < n; ++i)
#define fori(i, s, n) for (ll i = s; i > n; --i)
#define fora(i, n) for (auto i: n)
#define vi vector<int>
#define vll vector<ll>

const int MOD = 998244353;
// const int MOD = 1e9 + 7;

int find(string s, int l, int r, int deleted){
    if (deleted > 3) return 9999;
    if (l >= r) return deleted;
    while (l < r){
        if (s[l] != s[r]){
            return min(find(s,l+1,r,deleted+1),find(s,l,r-1,deleted+1));
        }
        l++;
        r--;
    }
    return deleted;
}


void solve() {
    string s;
    cin >> s;
    int deleted = find(s,0,s.length()-1,0);
    if (deleted == 9999){
        cout << "-1\n";
    } else {
        cout << deleted << endl;
    }
}

int32_t main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int t = 1;
    // cin >> t;
    while (t--) solve();

    return 0;
}