#include <bits/stdc++.h>
using namespace std;
int main()
{
    string string;
    int sum;
    sum = 0;
    cin >> string;
    for (int i = 0; i < string.size() - 2; i++)
    {
        if (string[i] == string[i + 1] && string[i + 1] != string[i + 2])
        {
            sum = sum + 1;
        };
        if (
            string[i] != string[i + 1] && string[i + 1] == string[i + 2])
        {
            sum = sum + 1;
        };
    }
    cout << sum;
}