typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main(){
    // BB -> 1
    // AA -> every 1
    // BA -> 1
    // AB -> if BAB -> 0
            //  AAB -> 1
    ll n;
    std::cin >> n;
    string s;
    std::cin >> s;
    ll bb = 0;
    ll ans= 0;
    for (int i = 0; i < n-1; i++) {
        if(s[i]=='B'&&s[i+1]=='B'){
            bb=1;
        }else if(s[i]=='B'){
            ans++;
        }else if(s[i+1]=='B'){
            if(i==0||s[i-1]=='A'){
                ans++;
            }
        }else{
            ans++;
        }
    }
    std::cout << ans+bb << std::endl;
}