Understand Boxing And Unboxing In C#

using System;
class BoxUboxTest {
    static void Main(string[] args) {
        int m = 10;
        object a = m; // boxing
        try {
            Console.WriteLine("Value of m is:" + a);
            // unbox
            object n = 20;
            int b = (int) n;
            Console.WriteLine("Value of n is:" + b);
            System.Console.WriteLine("Unboxing OK.");
            Console.ReadKey();
        } catch (System.InvalidCastException e) {
            System.Console.WriteLine("Error: Incorrect unboxing." + e.Message);
        }
    }
}