while True:
    H,W = map(int,raw_input().split())
    if H == 0 and W == 0:
        break
    for i in range(0,H/2):
        print ("#."* (W/2) + "#"* (W%2))
        print (".#"* (W/2) + "."* (W%2))
    if H%2 == 1:
        print ("#."* (W/2) + "#"* (W%2))
    print""


         