while True:
    H, W = map(int, raw_input().split())
    if H == W == 0:
        break
    for i in range(H):
        if i % 2 == 0:
            print "#" + ".#" * (W-2) + "#" * (W%2)
        else:
            print "." + "#." * (W-2) + "." * (W%2)
