while True:
    h,w = map(int,input().split())

    if h==0 and w==0:
        break

    for i in range(h):
        if i%2==0:
            if w%2==0:
                print("#."*(w-2))
            else:
                print("#."*(w-2)+"#")
        else:
            if(w%2==0):
                print(".#"*(w-2))
            else:
                print(".#"*(w-2)+".")