/* -*- coding: utf-8 -*-
 *
 * 2021.cc:  No.2021 Not A but B - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

/* global variables */

char s[MAX_N + 4];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d%s", &n, s);

  int c = 0, d = 0;
  for (int i = 0; i < n;) {
    int j = i;
    while (i < n && s[i] == 'B') i++;
    if (i - j >= 2) d = 1;
    if (i >= n) break;

    j = i;
    while (i < n && s[i] == 'A') i++;

    int l = i - j;
    if (l == 1) c++;
    else c += (l + 1) - (j == 0 ? 1 : 0) - (i == n ? 1 : 0);
  }

  printf("%d\n", c + d);
  return 0;
}