#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
using namespace std;


int main()
{
    int n, sum1 = 0;
    cin >> n;
    vector<int> v(n+1, 1);
    for (int i = 2; i <= n; i++){
        if (v[i]){
            for (int j = i*i; j <= n; j += i){
            v[j] = 0;
            }
        }
    }
    for (int i = 2; i <= n; i++){
        if(v[i]) sum1 += i;
    }
    cout << sum1 << endl;
}