#include <iostream>
#include <string>
using namespace std;

int main() {
    int N;
    string s;
    cin >> N >> s;
    
    int max_count = 0;
    int current_count = 0;
    
    for (char c : s) {
        if (c == 'A') {
            current_count++;
            if (current_count > max_count) {
                max_count = current_count;
            }
        } else {
            current_count = 0;
        }
    }
    
    cout << max_count << endl;
    return 0;
}