n,k = map(int,input().split())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
l = []
for i in range(n):
    
    l.append([a[i],b[i],a[i]-b[i],i])
l.sort(key = lambda x:-x[2])
ans = []
for i in range(n):
    a,b,sa,idx = l[i]
    if i + 1 <= k:
        ans.append(["A",idx])
    else:
        ans.append(["B",idx])
ans.sort(key = lambda x:x[1])
ans2 = []
for i in range(n):
    ans2.append(ans[i][0])
print("".join(ans2))