# Print a Chessboard

end = 0
while end == 0:
    rectangle = [int(i) for i in input().rstrip().split()]
    height = rectangle[0]
    width = rectangle[1]
    if [height, width] == [0, 0]:
        end += 1
    else:
        for i in range(height):
            for j in range(width):
                sum = i + j
                if sum % 2 == 0:
                    print('#', end = "")
                elif sum % 2 == 1:
                    print('.', end = "")
            print()

