using System;

​

public class Program

{

    public static void Main()

    {   

        var result = SquareDigits(9119);

        Console.WriteLine("811181" + " and result is: " + result);

    }

​

    public static int SquareDigits(int n)

    {

        char[] numbers = n.ToString().ToCharArray();

        string result = "";

        foreach(var num in numbers){

            int number = int.Parse(num.ToString());

            result = result + (number * number).ToString();

        }

        return int.Parse(result);

    }

}