#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)

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

    int n = s.size(), ans = 0;
    rep(i,n-2){
        if(s[i]==s[i+1] && s[i+1]!=s[i+2]) ans++;
        if(s[i]!=s[i+1] && s[i+1]==s[i+2]) ans++;
    }

    cout << ans << endl;

}