//Normal

#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

void print(auto a){
  cout << a;
}

void prints(auto a){
  cout << a << " ";
}

void prints(){
  cout << " ";
}

void printl(auto a){
  cout << a << endl;
}

void printl(){
  cout << endl;
}

void fix(int n){
  cout << fixed << setprecision(n);
}

int siz(string s){
  return (int)s.size();
}

int main(){
  int N; cin >> N;
  int ans = 0;

  for(int i = 2; i <= N; i++){
    bool flag = true;

    for(int j = 2; j*j <= i; j++){
      if(i%j == 0){
        flag = false;
        break;
      }
    }

    if(flag) ans += i;
  }

  printl(ans);

  return 0;
}