import java.math.BigInteger;
import java.util.Scanner;

class Main {
	public static void main(String[] args) {
		new Main().run();
	}

	void run() {
		Scanner sc = new Scanner(System.in);
		long ans = 0;
		int N = sc.nextInt();
		for (int i = 2; i <= N; ++i)
			if (BigInteger.valueOf(i).isProbablePrime(20))
				ans += i;
		System.out.println(ans);
	}

}