#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) {
	if (n == 2) {
		return true;
	}
	else {
		for (int i = 2; i <= n - 1; ++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 (prime(i)) { ans += i; }
	}
	cout << ans << endl;
}