import java.util.Scanner;

class Main{
	public static void main(String[] args) {
		Scanner scan=new Scanner (System.in);
		int n=scan.nextInt(),s=0,i,j;
		scan.close();
		for(i=2;i<=n;i++) {
			for(j=2;j<=(int)Math.sqrt(i);j++) if(i%j==0) break;
			if(j==(int)Math.sqrt(i)+1) s+=i;
		}
		System.out.print(s);
	}
}