#include <iostream>
#include <math.h>
using namespace std;

int n;
int ans;
int main() {
	cin >> n;
	for (int i = 2; i <= n; i++) {
		bool flag = true;
		for (int j = 2; j <= sqrt(i); j++) {
			if (i%j != 0)continue;
			else { flag = false; break; }
		}
		if (flag)ans += i;
	}
	cout << ans << endl;
	return 0;
}