n,k = map(int,input().split())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
c = [-1]*n
ab = []
for i in range(n):
	ab.append([a[i],i,0])
	ab.append([b[i],i,1])
from operator import itemgetter
ab.sort(key=itemgetter(0),reverse=True)
cnt = [k,n-k]
for s,t,u in ab:
	if c[t]==-1:
		if cnt[u]>0:
			c[t] = u
			cnt[u] -= 1
ans = ''.join([chr(ord('A')+i) for i in c])
print(ans)