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

int main(){
	int n;
	char s;
	cin>>n;
	
	int c = 0;//计数器
	int m = 0;//最多出现的次数
	int i;
	for(i = 0;i < n;i++){
		cin>>s;
		if(s == 'A'){
			c++;
			if(c > m){
				m = c;
			} 
		}else{
			c = 0;
		}
	} 
	
	cout<<m<<endl;
	return 0;
}


/**************************************************************
	Problem: 1540
	User: admin
	Language: C++
	Result: Accepted
	Time:79 ms
	Memory:2072 kb
****************************************************************/