n,k = map(int,input().split())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
choice = [1]*n
d = [[a[i]-b[i],i] for i in range(n)]
from operator import itemgetter
d.sort(key=itemgetter(0),reverse=True)
for i in range(k):
	choice[d[i][1]] = 0
print(''.join([chr(ord('A')+i) for i in choice]))