import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
		int ans = 0;
		for(int i = n ; n >= 2 ; i-- ){
			boolean flg = false;
			for(int j = i - 1 ; j >= 2 ; j--){
				if(i != j && i % j == 0){
					flg = true;
					break;
				}
			}
			if(!flg){
				ans += i;
			}
		}
        System.out.println(ans);
    }
}