#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<stack>
#include<cmath>
#include<cstdlib>
#include<ctime>
using namespace std;
typedef long long ll;
int main() {
	int n;
	ll sum = 0;
	cin >> n;
	for (int i = 2; i <= n; i++) {
		for (int j = 2; j <= sqrt(i); j++) {
			if (!(i%j))goto age;
		}
		sum += i;
	age:;
	}
	cout << sum << endl;
	return 0;
}