using System;

public class Program

{

    public static void Main()

    {

        int [] numArray = {1, 2, 3, 4};

        // To check if the value 3 exists in the array, you write

        int result = Array.IndexOf(numArray, 3);

        Console.WriteLine(result); // Prints 2

        // If you write

        int result1 = Array.IndexOf(numArray, 5);

        Console.WriteLine(result1); // Prints -1

        // The value of result is -1 because 5 does not exist in the numArray.

    }

}