write a code for JNTUH CGPA to Percentage calculator

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace HelloWorld
{
public class Program
{
public static void Main (string[]args)
{

     int a= int.Parse(Console.ReadLine());
	 int b= int.Parse(Console.ReadLine());
	 int c= int.Parse(Console.ReadLine());
	 int d= int.Parse(Console.ReadLine());
if (a>=0 && a<=1000 && b>=0 && b<=1000 && c>=0 && c<=1000 && d>=0 && d<=1000)
{
  if (a>b && a>c && a>d)
    {
    Console.WriteLine(a);
 	  }
    else if (b>a && b>c && b>d)
    {
    Console.WriteLine(b);
    }
    else if(c>a && c>b && c>d)
    {
    Console.WriteLine(c);
    }
    else
    {
    Console.WriteLine(d);
    }
  } 
  
  
  this is a dummy code any one plz write