n,k = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
ans = ["B"]*n
L = [[a-b,i] for i,(a,b) in enumerate(zip(A,B))]
L.sort(reverse=True)
for i in range(k):
    ans[L[i][1]] = "A"
print(*ans,sep="")