Gravity SFML

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

    sf::Time time = sf::seconds(0);
    sf::Clock timer;

    sf::Vector2f velocity(0, 3);
    int gravity = 1;

    sf::RectangleShape square;
    square.setSize(sf::Vector2f(40, 40));
    square.setFillColor(sf::Color::Blue);
    square.setPosition(400, 0);

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

        time = timer.getElapsedTime();
        if (time.asSeconds() > .3)
        {
            timer.restart();
            velocity.y += gravity;
        }

        square.move(velocity);

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

        window.draw(square);

        window.display(); //Display
    }

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