Unknown Identifier SceneManager/Obsolete Application.LoadLevel

#pragma strict

if(Input.GetKeyDown(KeyCode.Alpha1)||Input.GetKeyDown(KeyCode.Keypad1)){
    SceneManager.LoadScene(1);
}
if(Input.GetKeyDown(KeyCode.Alpha2)||Input.GetKeyDown(KeyCode.Keypad2)){
    Application.Quit();
}

When I use Application.LoadLevel, it’s obsolete. SceneManager is unknown. Why!!!

Add “using UnityEngine.SceneManagement;” to your script to use SceneManager,