#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    string s;
    cin >> s;
    int n = s.size(), ans = 0;
    for(int i = 0; i + 3 <= n; i++){
        ans += (s[i] == s[i + 1] || s[i + 1] == s[i + 2]) && s[i] != s[i + 2];
    }
    cout << ans << '\n';
}