import java.util.*;

public class Main {
	public static void main (String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		TreeSet<Integer> primeSet = new TreeSet<>();
		int total = 0;
		for (int i = 2; i <= n; i++) {
		    if (isPrime(i, primeSet)) {
		        total += i;
		        primeSet.add(i);
		    }
		}
		System.out.println(total);
	}
	
	static boolean isPrime(int x, TreeSet<Integer> set) {
	    for (int y : set) {
	        if (y > Math.sqrt(x)) {
	            break;
	        }
	        if (x % y == 0) {
	            return false;
	        }
	    }
	    return true;
	}
}