#include <iostream>
#include <cstdio>
using namespace std;
const int N = 1e3 + 5;

int f[N][N];
string str;

int dfs(int l, int r)
{
    if (f[l][r]) 
        return f[l][r];
    if (l >= r)
        return 0;
    int res;
    if (str[l] != str[r])
        res = min(dfs(l, r-1)+1, dfs(l+1, r)+1);
    else
        res = dfs(l+1, r-1);
    return f[l][r] = res;
}

int main()
{
    cin >> str;
    cout << dfs(0, str.size()-1);
    return 0;
}