Sieve of Eratosthenes

using System;
using System.Linq;

namespace ConsoleApp5
{
    class Program
    {
        static void Main(string[] args)
        {
            int input = int.Parse(Console.ReadLine());

            string arrString = "";

            for (int i = 2; i <= input; i++)
            {
                bool isPrime = true;

                for (int j = 2; j <= Math.Sqrt(i); j++)
                {
                    if (i % j == 0)
                    {
                        isPrime = false;
                    }
                }

                if (isPrime)
                {
                    arrString += i + " ";
                }

            }

            int[] arr = arrString.Split(' ').Select(int.Parse).ToArray();

            Console.WriteLine(string.Join(" ", arrString));
        }
    }
}