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


int main(){
                                                                     

    int n, i, j;

    int k = 0;

    int f = 1;


    cin >> n;


    for( i = 2 ; i <= n ; i = i + 1 ){

         f = 1;

         for( j = 2 ; j < i ; j = j + 1 ){

              if( i % j == 0 ) f = 0;

              }

         if( f == 1 ) k += i;

         }


    cout << k << endl;
    

    return 0;

    }