#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 = 300500, inf = 1e9, 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);
}
string s;
const int maxN = 105;
int n;
int dp[maxN][2][2];
const int INF = 1e9;
void solve() {
    cin >> s;
    n = s.size();
    for (int i = 0; i <= n; i++) {
        for (int j = 0; j < 2; j++) {
            for (int k = 0; k < 2; k++) {
                dp[i][j][k] = INF;
            }
        }
    }
    //i, i + 1
    //n - i - 1
    dp[0][0][0] = 0;
    for (int i = 0; i <= (n - 1) / 2; i++) {
        for (int x = 0; x < 2; x++) {
            for (int y = 0; y < 2; y++) {
                if (dp[i][x][y] == INF) continue;
                for (int A = 0; A < 2; A++) {
                    for (int B = 0; B < 2; B++) {
                        if (n % 2 == 0 && (i == (n - 1) / 2) && (A != B)) continue;
                        int add = A + B;
                        if (n % 2 == 0 && (i == (n - 1) / 2)) add -= A;
                        int opL = x + A;
                        int opR = y + B;
                        bool can = false;
                        for (int z = 0; z < 26; z++) {
                            int L = s[i] - 'a';
                            int R = s[n - 1 - i] - 'a';
                            if (n % 2 == 1 && i == (n - 1) / 2) {
                                can = true;
                                break;
                            }
                            if (opL >= 2 || (((L != z) && opL == 1)) || (L == z && opL == 0)) {
                                if (opR >= 2 || (((R != z) && opR == 1)) || (R == z && opR == 0)) {
                                    can = true;
                                    break;
                                }
                            }
                        }
                        if (can) {
                            dp[i + 1][A][B] = min(dp[i + 1][A][B], dp[i][x][y] + add);
                        }
                    }
                }
            }
        }
    }
    int best = 1e9;
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            best = min(best, dp[(n + 1) / 2][i][j]);
        }
    }
    cout << best;
}

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();
    }
}