import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        boolean[] isNotPrimes = new boolean[n + 1];
        isNotPrimes[0] = true;
        isNotPrimes[1] = true;
        for (int i = 2; i <= n; i++) {
            if (!isNotPrimes[i]) {
                for (int j = 2; i * j <= n; j++) {
                    isNotPrimes[i * j] = true;
                }
            }
        }
        long sum = 0;
        for (int i = 2; i <= n; i++) {
            if (!isNotPrimes[i]) {
                sum += i;
            }
        }
        System.out.println(sum);
    }
}