#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
using namespace std;

using ll = long long;
const int INF = 1e9;
const ll inf = 1LL<<62;

void solve() {
  int n; cin >> n;
  string s; cin >> s;
  set<pair<int, int>> S;
  for (int i=0; i+1<n; i++) {
    if (s[i] == 'A' && s[i+1] == 'A') {
      S.insert({i, i+1});
    } else if (s[i] == 'A') {
      S.insert({i, -1});
    } else if (s[i+1] == 'A') {
      S.insert({i+1, -1});
    } else {
      S.insert({-1, -1});
    }
  }
  cout << S.size() << '\n';
}

int main() {
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  // int t; cin >> t;
  /*while (t--)*/ solve();
}