import sys
from math import factorial

def solve():
    n, d = map(int, input().split())

    if d == 0:
        print('C'*n)
        return

    if d == 1:
        ans = 'A' + 'C' * (n - 1)
        print(ans)
        return

    if n <= d <= 2*n:
        k = (2*n - d)
        ans = 'A' * k + 'B' * (n - k)
        print(ans)
    else:
        ans = 'A' * d + 'C' * (n - d)
        print(ans)


if __name__ == '__main__':
    solve()