import math
while True:
    H, W = map(int, input().split())
    if H == 0 and W == 0:
        break

    if H == 1 and W == 1:
        print('#')
    else:
        for x in range(1, H+1):
            if x % 2 != 0:
                print('{0}'.format('#.' * math.ceil(W/2)))
            else:
                print('{0}'.format('.#' * math.ceil(W/2)))
    print('')

