#include <iostream>
#include <string>

using namespace std;

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

    int cnt = 0;
    bool start = false;

    for(int i = 0; i < s.length()-1; i++) {
        if(s[i+1] == s[i] && !start) {
            start = true;
        } else if(s[i+1] == s[i] && start) {
            cnt++;
            start = false;
        }
    }

    if(start) {
        cnt++;
    }

    cout << cnt << endl;

    return 0;
}