#include <algorithm>
#include <array>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <numeric>
#include <optional>
#include <queue>
#include <set>
#include <sstream>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

int main() {
    int32_t n;
    cin >> n;
    vector<bool> ps(n + 1, true);
    ps[0] = ps[1] = false;
    for (auto i = 2; i * i <= n; ++i) {
        if (!ps[i])
            continue;
        for (auto j = i * 2; j <= n; j += i) {
            ps[j] = false;
        }
    }
    int32_t ans = 0;
    for (auto i = 0; i <= n; ++i) {
        if (ps[i])
            ans += i;
    }
    cout << ans << endl;
    return 0;
}