n,k=map(int,input().split())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
tmp=[]
s=["A"]*n
for i in range(n):
    tmp.append([a[i]-b[i],i])
tmp.sort()
for j in range(n-k):
    s[tmp[j][1]]="B"
print("".join(s))