#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <stdio.h>
#include <cstring>
#include <queue>
#include <stack>
#include <functional>
#include <math.h>
using namespace std;
#define Would
#define you

bool prime(int n) {
	for (int i = 2; i < sqrt(n); ++i) {
		if (n%i != 0) {
			return false;
		}
	}
	return true;
}

int ans;
int main() {
	int n;
	cin >> n;
	for (int i = 2; i <= n; ++i) {
		if (i == 2) { ans += i; }
		if (prime(i)) { ans += i; }
	}
	cout << ans << endl;
}