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

using ll = long long;

int main(){
  string s; cin >> s;
  ll ans = 0;
  cerr << s << endl;
  for(ll i=0; i<=s.length()-3; i++){
    cerr << s[i] << s[i+1] << s[i+2] << " ";
    if((s[i] == s[i+1] && s[i+1] != s[i+2]) || (s[i] != s[i+1] && s[i+1] == s[i+2])){
      ans++;
      cerr << "good";
    }
    cerr << endl;
  }
  cout << ans << endl;
}