C++ :

#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;
}

Java :

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num1 = scanner.nextInt();
        String str = new String();
        int[] b = new int[num1];
        int[] count = new int[100];
        double avg;
        int max = 0;
        int x = 0,m = 0;
            str = scanner.next();
        char a[] = str.toCharArray();
        for (int i = 0; i < num1; i++) {
            if(a[i] == 'A'){
                m++;
                if(max < m)max = m;
            }else{
                m = 0;
            }

        }
        System.out.println(max);
    }

    public static boolean judge(int i,int j){
        int a,s = 0;
        while(i != 0){
            a = i % 10;
            s = s + a;
            i /= 10;
        }
        if(s == j)return true;
        else return false;
    }

    public static void paiXux(int[] a){
        int temp;
        for(int i = 0;i < a.length - 1;i++){
            for(int k = 0;k < a.length - i - 1;k++){
                if(a[k] > a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    }public static void paiXu(int[] a,int length){
        int temp;
        for(int i = 0;i < length - 1;i++){
            for(int k = 0;k < length - i - 1;k++){
                if(a[k] > a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    } public static void paiXud(int[] a){
        int temp;
        for(int i = 0;i < a.length - 1;i++){
            for(int k = 0;k < a.length - i - 1;k++){
                if(a[k] < a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    }

    public static int MAX(int[] a){
        int max = a[0];
        for (int i = 0; i < a.length; i++) {
            if(max < a[i]){
                max = a[i];
            }
        }
        return max;
    }

    public static int MIN(int[] a){
        int min = a[0];
        for (int i = 0; i < a.length; i++) {
            if(min > a[i]){
               min = a[i];
            }
        }
        return min;
    }
    public static int sum(int a){
        int x,s = 0;
        while(a != 0){
            x = a % 10;
            s = s + x;
            a /= 10;
        }
        return s;
    }
    public static boolean isPrime(int a){
        if(a <= 1)return false;
        else
        for(int i = 2;i <= Math.sqrt(a);i++){
            if(a % i == 0)return false;
        }return true;
    }

    public static int qiuYu(int i){
        int a;
        a = i % 10;
        return a;
    }
}

Python :

n=int(input())
a=input()
da=0
k=0
for i in range(len(a)):
    x2=a[i:i+1]
    if(x2=="A"):
        k=k+1
        if(k>da):
            da=k
    else:
        k=0
print(da)