// yukicoder No.713
#include <bits/stdc++.h>
using namespace std;

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

    int sum = 0;

    for (int i = 2; i <= n; ++i) {
        bool flag = true;
        int lim = sqrt(i);
        for (int j = 2; j <= lim; ++j) {
            if (i % j != 0) continue;
            else {
                flag = false;
                break;
            }
        } 

        if (flag) sum += i;
        else continue;
    }

    cout << sum << "\n";

    return 0;
}