#include <bits/stdc++.h>
#define ll long long
using namespace std;
#define all(v) v.begin(), v.end()
#define rep(i,n) for (long long i=0;i<(long long)(n);i++)

int main() {
    int N;
    string S;
    cin >> N >> S;
    int ans=0;
    bool not_henka=false;
    rep(i,N-1){
        if(S[i+1] == 'A')ans++;
        else if(/*S[i+1]=='B'&&*/S[i] == 'A' &&(i == 0 || S[i-1] == 'A')) ans++;
        else if(S[i] == S[i+1] && S[i] == 'B')not_henka = true;
    }
    cout << ans+not_henka << endl;
}