#include<bits/stdc++.h>
using namespace std;

#define rep(i, a, n) for(int i=(a); i<(n); ++i)
#define per(i, a, n) for(int i=(a); i>(n); --i)
#define pb emplace_back
#define mp make_pair
#define clr(a, b) memset(a, b, sizeof(a))
#define all(x) (x).begin(),(x).end()
#define lowbit(x) (x & -x)
#define fi first
#define se second
#define lson o<<1
#define rson o<<1|1
#define gmid l[o]+r[o]>>1

using ll = long long;
using ull = unsigned long long;
using pii = pair<int,int>;
using pll = pair<ll, ll>;
using ui = unsigned int;

constexpr int mod = 1e9 + 7;
constexpr int MOD = 998244353;
constexpr int inf = 0x3f3f3f3f;
constexpr double eps = 1e-8;

const int N = 2e5 + 10;

int n, ans;
char s[N];

int main(){
  scanf("%d", &n);
  scanf("%s", s);
  ans = 0;
  bool keep = 0;
  rep(i, 1, n){
    if(s[i-1] == 'B' && s[i] == 'B'){
      keep = 1;
    } else if(s[i] == 'A'){
      ans += 1;
    } else if(s[i-1] == 'A' && (i <= 1 || s[i-2] == 'A')){
      ans += 1;
    }
  }
  printf("%d\n", ans + keep);
  
  return 0;
}