#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int n = s.size(), cnt = 0, flag = 0;
  for (int i = 0; i < (n - 1); ++i) {
    if (s[i] == s[i + 1]) {
      if (flag == 0) {
        flag = 1;
        continue;
      } else
        flag = 0;
    }
    cnt++;
  }
  cout << cnt;
}
