#include <iostream>

using namespace std;

int main() {
    string s;
    cin >> s;

    long long ans = 0;
    for (int i = 0; i < s.size() - 2; i++) {
        if (s[i] == s[i + 1] && s[i] != s[i + 2]) {
            ans++;
        }
        else if (s[i] != s[i + 1] && s[i + 1] == s[i + 2]) {
            ans++;
        }
    }

    cout << ans << endl;
}