Gravity Model SFML

int main()
{
    sf::RenderWindow window(sf::VideoMode(800, 600), "In Development");
    window.setFramerateLimit(70);
    window.setVerticalSyncEnabled(true);

    sf::RectangleShape square;
    square.setSize(sf::Vector2f(50, 50));
    square.setFillColor(sf::Color::Blue);
    square.setPosition(400, 300);

    sf::Vector2f velocity(0, 0);

    int jumpSpeed = 10, gravity = 1;

    sf::Event event;
    while (window.isOpen())
    {
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed)
                window.close();
        }

        if (sf::Keyboard::isKeyPressed(sf::Keyboard::Up))
        {
            velocity.y = -jumpSpeed;
        }
        else if (sf::Keyboard::isKeyPressed(sf::Keyboard::Right))
        {
            velocity.x = jumpSpeed;
        }
        else if (sf::Keyboard::isKeyPressed(sf::Keyboard::Left))
        {
            velocity.x = -jumpSpeed;
        }
        else
        {
            velocity.y += gravity;
            velocity.x = 0;
        }

        square.move(velocity);

        if (square.getPosition().y >= 500)
        {
            square.setPosition(square.getPosition().x, 500);
        }

        window.clear(sf::Color::White); //Clear

        window.draw(square);

        window.display(); //Display
    }

    int pause; cin >> pause; //Pause the program
    return 0;
}