matrix = []
while True:
    values = input()
    if '0 0' == values:
        break
    matrix.append([int(x) for x in values.split()])

for height, width in matrix:
    if 1 == height and 1 == width:
        print('#')
        print()
        continue
    for i in range(height):
        if 0 == i % 2:
            print('#.' * (width // 2))
        else:
            print('.#' * (width // 2))
    print()