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

int main(){
  string s;
  cin>>s;
  int n=s.size();
  int ans=0;
  for (int i=0;i<n-2;i++){
    char c1=s[i],c2=s[i+1],c3=s[i+2];
    if ((c1==c2&&c2!=c3)||(c2==c3&&c1!=c2)) ans++;
  }
  cout<<ans<<endl;
}