def chess(h,w):
  if(h+w) % 2 == 0:
    return '#'
  return '.'

while True:
  H , W = map(int, input().split())
  if H == 0 and W == 0:
    break
    for i in range(H):
      for j in range(W):
        print(chess(i,j), end='')
        print()
        print()
