using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

     string aplhaNumeric = "uyu7u123abc";   

        char[] newAplhaNumeric = aplhaNumeric.ToCharArray();

            string newLetter ="";           

        foreach(char c in newAplhaNumeric){

            if(char.IsNumber(c))

            {   

                newLetter += c.ToString();

            }

        }

            Console.WriteLine( "Alpha numeric string " +aplhaNumeric);  

            Console.WriteLine("numeric string " +newLetter);            

    }

}