import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		int sum = 0;
		for(int i = 1; i <= N; i++) {
			if(isPrime(i)) {
				sum += i;
			}
		}
		scan.close();
		System.out.println(sum);
	}
 public static boolean isPrime(long n) {
        if(n == 1) {
        	return false;
        }
        for(long i = 2; i <= (int)Math.sqrt(n); i++){
            if(n % i == 0) {
                return false;
            }
        }
        return true;
    }
}