#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int ans = 0;
  bool ok = false;
  for (int i = 0; i < n - 1; i++) {
    if (s[i] == 'A' && s[i + 1] == 'A') ans++;
    if (s[i] == 'A' && s[i + 1] == 'B') ans++;
    if (s[i] == 'B' && s[i + 1] == 'A') ans++;
    if (s[i] == 'B' && s[i + 1] == 'B') ok = true;
  }
  if (ok) ans++;
  int cnt = 0;
  for (int i = 0; i < n - 2; i++) {
    if (s[i] == 'B' && s[i + 1] == 'A' && s[i + 2] == 'B') cnt++;
  }
  cout << ans - cnt << endl;
  return 0;
}