# -*- coding: utf-8 -*-

N, D = map(int, input().split())

diff = D - N
answer = ''

#穴1と穴2が混在
if diff > 0:
    answer = 'A' * (2*N-D)
    temp = 'B' * diff
    answer += temp
#穴1のみ
elif diff == 0:
    answer = 'A' * N
#穴1と穴0が混在
else:
    answer = 'A' * D
    temp = 'C' * (N-D)
    answer += temp

print(answer)