///Enta etfsh5t nseet el rank

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,fma")

#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update

using namespace std;
using namespace __gnu_pbds;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,
        tree_order_statistics_node_update>;
#define pb push_back
#define F first
#define S second
#define f(i, a, b) for (int i = a; i < b; i++)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define sz(x) (int)(x).size()
//#define mp(x, y) make_pair(x, y)
#define popCnt(x) (__builtin_popcountll(x))
#define int ll

using ll = long long;
using ull = unsigned long long;
using uint = uint32_t;
using ii = pair<int, int>;

const int N = 1e5 + 20, LG = 18, MOD = (119 << 23) + 1;
const long double PI = acos(-1);

const long double EPS = 1e-9;

int dp[105][105][2][2];
string s;
int n;

bool checkEqual(int a, int b, bool f1, bool f2) {
    if (!f1 && !f2)
        return s[a] == s[b];
    if (f1 || f2)
        return s[a] != s[b];
    return true;
}

int solve(int l, int r, bool goL, bool goR) {
    if (l == r)
        return 0;
    if (l + 1 == r || l + 2 == r) {
        if (checkEqual(l, r, goL, goR))
            return 0;
        return 1;
    }
    int &ret = dp[l][r][goL][goR];
    if (~ret)
        return ret;
    ret = 1e9;
    if (checkEqual(l, r, goL, goR))
        ret = solve(l + 1, r - 1, 0, 0);
    for (char c = 'a'; c <= 'z'; c++) {
        bool ngL, ngR;
        if (goL == true) {
            if (s[l] == c)ngL = true;
            else ngL = false;
        } else {
            if (s[l] == c)ngL = false;
            else ngL = true;
        }
        if (goR == true) {
            if (s[r] == c)ngR = true;
            else ngR = false;
        } else {
            if (s[r] == c)ngR = false;
            else ngR = true;
        }
        ret = min(ret, solve(l + 1, r - 1, ngL, ngR) + int(ngL) + int(ngR));
    }
    return ret;
}

void doWork() {

    cin >> s;
    n = s.size();
    ::memset(dp, -1, sizeof dp);
    cout << solve(0, n - 1, 0, 0) << '\n';

}

int32_t main() {
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0);
    cin.tie(0);
#endif // ONLINE_JUDGE
    int t = 1;
//    cin >> t;
    while (t--)
        doWork();
    return 0;
}