#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

void shave(vector<int> &v, int n)
{
    vector<int> x, y;
    int n_sq = sqrt(n) + 1;
    for (int i = 3; i < n + 1; i += 2)
    {
        x.push_back(i);
    }
    for (int i = 3; i < n_sq; i += 2)
    {
        for (auto itr = x.begin(); itr != x.end(); itr++)
        {
            if (*itr == i || *itr % i != 0)
                y.push_back(*itr);
        }
        x.clear();
        x = y;
        y.clear();
    }
    if (n >= 2)
        x.insert(x.begin(), 2);

    for (auto itr = x.begin(); itr != x.end(); itr++)
    {
        v.push_back(*itr);
    }
}

int main(){
    int n, ans;
    cin >> n;
    vector<int> primes;
    shave(primes, n);
    for (int x : primes)
        ans += x;
    cout << ans << endl;

    return 0;
}