import java.util.Scanner;

public class Main {

	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {

		int n = sc.nextInt();

		int index = 0;
		int[] prime = new int[n];

		int ans = 0;
		for(int i = 2; i <= n; i++) {
			boolean isPrime = true;
			for(int j = 0; j < index; j++) {
				if(i%prime[j] == 0) {
					isPrime = false;
					break;
				}
			}
			if(isPrime) {
				ans += i;
				prime[index] = i;
				index++;
			}
		}

		System.out.println(ans);
    }
}