#include <iostream>
#include <vector>

void solve() {
    int n;
    std::cin >> n;

    std::vector<bool> isp(n + 1, true);
    isp[0] = isp[1] = false;

    for (int p = 2; p * p <= n; ++p) {
        if (!isp[p]) continue;
        for (int q = p * 2; q <= n; q += p) {
            isp[q] = false;
        }
    }

    int ans = 0;
    for (int x = 0; x <= n; ++x) {
        if (isp[x]) ans += x;
    }

    std::cout << ans << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}