#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  char s[n];
  for (int i = 0; i < n; i++) cin >> s[i];
  int ans = 0;
  for (int i = 0; i < n - 1; i++) {
    if (s[i] != s[i + 1]) ans++;
  }
  if (ans > n - ans) ans = n - ans;
  cout << ans << endl;
  return 0;
}
