using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("enter the number");

        int n=int.Parse(Console.ReadLine());

        int r,sum=0;

        bool x=false;

        if(n>0){

        while(n>0){

            r=n%10;

            if(sum<r){

                sum=r;

                x=true;

            }

            n=n/10;

        }}

        if(x==true){

        Console.WriteLine(sum);

        }else

        {Console.WriteLine(" pasitive element enter  ");

        }

    }

}