#include <bits/stdc++.h>
#include <assert.h>

using namespace std;

int main()
{
	int n;
	cin >> n;
	int arr[1001];
	int ans = 0;
	for (int i = 0; i <= n; i++)
		arr[i] = 1;
	for (int i = 2; i < sqrt(n); i++)
		if (arr[i])
			for (int j = 0; i * (j + 2) <= n; j++)
				arr[i * (j + 2)] = 0;

	for (int i = 2; i <= n; i++)
		if (arr[i])
			ans += i;
	cout << ans << endl;

	return 0;
}