Колеги, може ли някой да помогне, че в Джъдж ми дава 70/100, а не си откривам грешката? Благодаря предварително.

това ми е кода:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp46
{
    class Program
    {
        static void Main(string[] args)
        {
            int primeN = 0;
            int nonPrimeN = 0;

            for (int i = 0; ; i++)
            {
                string n = Console.ReadLine();
                bool isPrime = true;

                if (n == "stop")
                {
                    break;
                }
                int num = int.Parse(n);

                if(num < 0)
                {
                    Console.WriteLine("Number is negative.");
                }
                else
                {
                    if (num < 2)
                    {
                        nonPrimeN += num;
                    }
                    for (int j = 2; j < num; j++)
                    {
                        if (num % j == 0)
                        {
                            isPrime = false;
                        }
                    }
                    if (isPrime == true)
                    {
                        primeN += num;
                    }
                    else
                    {
                        nonPrimeN += num;
                    }
                }
            }
            Console.WriteLine($"Sum of all prime numbers is: {primeN}");
            Console.WriteLine($"Sum of all non prime numbers is: {nonPrimeN}");
        }
    }
}