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)
        
/**************************************************************
	Problem: 1540
	User: admin
	Language: Python
	Result: Accepted
	Time:696 ms
	Memory:34488 kb
****************************************************************/