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