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 = 2 ; i < n ; i++ ){
			if(i % Math.sqrt(i) != 0){
				ans += i;
			}
		}
        System.out.println(ans);
    }
}