def perturb(cities, itinerary):
    neighborids1 = math.floor(np.random.rand() * (len(itinerary)))
    neighborids2 = math.floor(np.random.rand() * (len(itinerary)))

    itinerary2 = itinerary.copy()

    itinerary2[neighborids1] = itinerary[neighborids2]
    itinerary2[neighborids2] = itinerary[neighborids1]

    distance1 = howfar(genlines(cities, itinerary))
    distance2 = howfar(genlines(cities, itinerary2))

    itinerarytoreturn = itinerary.copy()

    if(distance1 > distance2):
        itinerarytoreturn = itinerary2.copy()

    return(itinerarytoreturn.copy())
