while True:
    a,b=input().split()
    h = int(a)
    w=int(b)
    if h==0 and w==0:
        break
    odd = "#."*300
    even= ".#"*300
    for i in range(h):
        if (i%2)==0:
            print(even[:w])
        else:
            print(odd[:w])
    print("")