from collections import deque
n,k = map(int,input().split())
a = list(map(int,input().split()))
b = list(map(int,input().split()))

lis = []
for i in range(n):
    diff = a[i] - b[i]
    lis.append([a[i],b[i],diff,i])
lis2 = sorted(lis,key=lambda x:x[2])[::-1]
select_a = set()
for i in range(k):
    select_a.add(lis2[i][3])
    
ans = deque()
for i in range(n):
    if(i in select_a):
        ans.append('A')
    else:
        ans.append('B')
print(''.join(ans))