#include<bits/stdc++.h>

using namespace std;

int main() {
  int N;
  cin >> N;
  string S;
  cin >> S;
  int ret = 0;
  int res = 0;
  int sub = 0;
  for(int i = 0; i + 1 < N; i++) {
    ret += S[i] == 'A' or S[i + 1] == 'A';
    res |= S[i] == 'B' and S[i + 1] == 'B';
  }
  for(int i = 0; i + 2 < N; i++) {
    sub += S[i] == 'B' and S[i + 1] == 'A' and S[i + 2] == 'B';
  }
  cout << ret + res - sub << endl;
}