import matplotlib.pyplot as plt


def bar_chart(numbers, labels, pos):
    plt.bar(pos, [4, 5, 6, 3], color="green")
    plt.bar(pos, numbers, color="blue")
    plt.xticks(ticks=pos, labels=labels)
    plt.title("Gas Used in Various Vehicles")
    plt.xlabel("Vehicle Types")
    plt.ylabel("Number of Vehicles")
    plt.show()


if __name__ == "__main__":
    numbers = [2, 1, 4, 6]
    labels = ["Electric", "Solar", "Diesel", "Unleaded"]
    pos = list(range(4))
    bar_chart(numbers, labels, pos)