#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	string s;
	cin>>n>>s;
	int cnt=0,ans=0;
	for(int i=0;i<s.size();i++){
		if(s[i]=='A') cnt++;
		else cnt=0;
		ans=max(ans,cnt);
	}
	cout<<ans<<endl;
}
/**************************************************************
	Problem: 1540
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:47 ms
	Memory:2388 kb
****************************************************************/