n,d=map(int,input().split())
t = n*2
ans = ['B']*n
for i in range(n):
    if t == d: break
    ans[i] = 'A'
    t -= 1
for i in range(n-1, -1, -1):
    if t == d: break
    ans[i] = 'C'
    t -=1
print(''.join(ans))