#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 1010;

int f[N][N];
string s;

int main()
{
    cin >> s;

    for (int len = 2; len <= s.size(); len ++ )
        for (int i = 0; i + len - 1 < s.size(); i ++ )
        {
            int j = i + len - 1;
            if (s[i] == s[j]) f[i][j] = f[i + 1][j - 1];
            else f[i][j] = min(f[i + 1][j], f[i][j - 1]) + 1;
        }

    cout << f[0][s.size() - 1] << endl;

    return 0;
}