#include<iostream>
#include<string>
#include<algorithm>
#include<functional>
#include<vector>
#include<set>
#include<queue>
#include<list>
#include<stdio.h>
#include<stdlib.h>
#include<map>

#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()

using namespace std;

vector<int> Eratosthenes(int n) {
	vector<int> a(n, 1);

	rep(i, 2, sqrt(n)) {
		if (a[i]) {
			for (int j = 0; i*(j + 2)< n; j++) {
				a[i*(j + 2)] = 0;
			}

		}
	}

	vector<int> primes;

	for (int i = 2; i < n; i++) {
		if (a[i]) {
			primes.push_back(i);
		}
	}
	
	return primes;
}

int main() {

	int n;
	cin >> n;

	auto ans = Eratosthenes(n+1);

	int sum = 0;
	fore(i, ans) {
		sum += i;
	}

	cout << sum << endl;

	return 0;
}