Fast Prime Checker

using System;

namespace P15_FastPrimeCheker
{
    class Program
    {
        static void Main(string[] args)
        {
            int n= int.Parse(Console.ReadLine());
            for (int num1 = 2; num1 <= n; num1++)
            {
                bool isPrime = true;
                for (int num2 = 2; num2 <= Math.Sqrt(num1); num2++)
                {
                    if (num1 % num2 == 0)
                    {
                        isPrime = false;
                        break;
                    }
                }
                Console.WriteLine($"{num1} -> {isPrime}");
            }

        }
    }
}