using System;

using System.Collections;

using System.IO;

internal static class Program

{

public static void Main(string[] args)

{

var n = args.Length > 0 ? int.Parse(args[0]) : 4;

for (var i = 0; i < 3; i++)

{

Sieve(10000 << (n - i));

}

}

private static void Sieve(int n)

{

var flags = new BitArray(n, false);

var count = 0;

for (var i = 2; i < n; i++)

{

if (!flags[i])

{

count += 1;

for (var j = i << 1; j < n; j += i)

{

flags[j] = true;

}

}

}

Console.WriteLine($"Primes up to {n,8} {count,8}");

}

}