5 part

def add_city_data(country, city, population, area):
    data = load_data()
    density = round(population / area, 2)
    if area
    else 0
    city_data = {"Core City": city, "Population": population, "Area": area, "Density": density}

    if country not in data:
        data[country] = []
    data[country].append(city_data)

    save_data(data)
    print(f"Data for {city}, {country} added successfully.")