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

zero = "C"
one = "A"
two = "B"

ans = []
while D and ( N - 1 - len( ans ) ) * 2 >= D - 1:
  ans += one
  D -= 1
while D >= 2:
  ans += two
  D -= 2
if D == 1:
  ans += one
  D -= 1
while len( ans ) < N:
  ans += zero

ans.sort()
print( ''.join( ans ) )