while True:
    H, W = map(int, input().split())
    if H == 0 and W == 0:
        break
    for x in range(H):
        if (x)%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) + ".")



