while True:
    x=input().split()
    W, H = int(x[0]), int(x[1])
    if W==0 and H==0:
        break
    hantei=True
    for i in range(W):
        if hantei:
            if H%2 == 0:
                print("#."*(H//2))
            elif H%2 == 1:
                print("#."*(H//2)+"#")
            hantei=False
        else:
            if H%2 == 0:
                print(".#"*(H//2))
            elif H%2 == 1:
                print(".#"*(H//2)+".")
            hantei = True