#include <bits/stdc++.h>
#define fi first
#define se second
#define bit(x) (1LL << (x))
#define getbit(x, i) (((x) >> (i)) & 1)
#define ALL(x) (x.begin(), x.end())
using namespace std;

template <typename T1, typename T2> bool maxi(T1 &a, T2 b) {
    if (a < b) {a = b; return true;} return false;
}

template <typename T1, typename T2> bool mini(T1 &a, T2 b) {
    if (a > b) {a = b; return true;} return false;
}

const int N = 2e5 + 5;
const int oo = 1e9;
const long long ooo = 1e18;

int main() {
    string s;
    cin >> s;
    if(s.size() == 1) {
        cout << 0 << endl;
        return 0;
    }
    bool ans[s.size() / 2];
    memset(ans, 0, sizeof(ans));
    for(int i = 0; i < s.size() / 2; ++i) {
        if(s[i] != s[s.size() - i - 1]) {
            ans[i] = 1;
        }
    }
    int res = 0;
    for(int i = 1; i < s.size() / 2; ++i) {
        if(ans[i - 1]) {
            res += 2;
            ans[i - 1] = 0, ans[i] = 0;
        }
    }
    if(ans[s.size() / 2 - 1])
        ++res;
    cout << res << endl;
}