n, d = map(int, input().split())

if n < d:
    b = d - n
    a = n - b
    c = 0
elif n > d:
    c = n - d
    a = n - c
    b = 0
else:
    a = n
    b = c = 0

print('A'*a + 'B'*b + 'C'*c)