#include <bits/stdc++.h>

#define f first
#define s second
#define pb push_back
#define mp make_pair

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;

const int N = 4300500, inf = 1e9;
const ll mod = 998244353;
const ll INF = 1e18;

int sum(int a, int b) {
    a += b;
    if (a >= mod)
        a -= mod;
    return a;
}

int sub(int a, int b) {
    a -= b;
    if (a < 0)
        a += mod;
    return a;
}

int mult(int a, int b) {
    return 1ll * a * b % mod;
}

int bp(int a, int b) {
    int res = 1;
    while (b) {
        if (b & 1)
            res = mult(res, a);
        a = mult(a, a);
        b >>= 1;
    }
    return res;
}

int inv(int x) {
    return bp(x, mod - 2);
}



int dp[N][7];

void solve() {
    string s;
    cin >> s;
    const int D = 3;
    int n = s.length();
    for (int i=0;i<=n;i++)
    {
        for (int j=0;j<=6;j++) dp[i][j] = mod;
    }
    dp[0][3] = 0;
    int A = mod;
    for (int i=0;i<=n;i++)
    {
        for (int b=-3;b<=3;b++)
        {
            if (dp[i][b+D]>3) continue;
            int L = i, R = n-1-i-b;
            if (L>R)
            {
                A = min(A,dp[i][b+D]);
                continue;
            }
            if (s[L]==s[R]) dp[i+1][b+D] = min(dp[i+1][b+D],dp[i][b+D]);
            if (dp[i][b+D]==3) continue;
            dp[i+1][b+D-1] = min(dp[i+1][b+D-1],dp[i][b+D]+1);
            dp[i][b+D+1] = min(dp[i][b+D+1],dp[i][b+D]+1);
        }
    }
    if (A==mod) A = -1;
    cout << A << "\n";
}

int main() {
#ifdef DEBUG
    freopen("input.txt", "r", stdin);
#endif
    ios_base::sync_with_stdio(false);
    int t = 1;
//    cin >> t;
    for (int i = 1; i <= t; i++) {
//        cout << "Case #" << i << endl;
        solve();
    }
}