How to generate a number with "Random.range" to change scene?

I have this script:

public class EmpezarJuego : MonoBehaviour {

int number;

public void Empezar() {

    number = Random.Range(1,4);

    if (number == 1) {
        SceneManager.LoadScene ("GAME");
    }
    if (number == 2) {
        SceneManager.LoadScene ("GAME_1");
    }
    if (number == 3) {
        SceneManager.LoadScene ("GAME_2");
    }
    if (number == 4) {
        SceneManager.LoadScene ("GAME_3");
    }



 }
}

I want: If number = 1, my scene is GAME, if number = 2, then, my scene is GAME_1 .... BUT it NOT WORKS why??