#include <bits/stdc++.h>
using namespace std;

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

    int n;
    cin >> n;

    vector<bool> F(n + 1, true);
    F[0] = F[1] = false;
    for(int i = 2; i <= (int)(sqrt(n)); i++){
        if(F[i])
            for(int j = i + i; j <= n; j += i){
                F[j] = false;
            }
    }

    int ans = 0;
    for(int i = 2; i <= n; i++){
        if(F[i]) ans += i;
    }

    cout << ans << endl;

    return 0;
}