#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

vector<int> prime_vector(int n) {
    int m = (int)sqrt(n - 1);

    vector<bool> q(n);
    for (int i = 2; i <= m; i++) {
        if (q[i]) continue;
        for (int j = i * i; j < n; j += i) {
            q[j] = true;
        }
    }

    vector<int> p; p.reserve(n / log(n * 0.329));
    for (int i = 2; i < n; i++) {
        if (!q[i]) p.push_back(i);
    }
    return p;
}

int main() {
    int n;
    cin >> n;

    auto pv = prime_vector(max(n, 10) + 1);

    int r = 0;
    for (auto& p : pv) {
        if (p > n) break;
        r += p;
    }

    cout << r << endl;

    return 0;
}