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

int main(){
  vector<bool> Era(1001, true);
  Era[0] = Era[1] = false;
  for(int i = 2; i*i <= 1000; i++){
    if(!Era[i]) continue;
    for(int j = i*2; j <= 1000; j += i){
      Era[j] = false;
    }
  }
  int N; cin >> N;
  int ans = 0;
  for(int i = 1; i <= N; i++){
    if(Era[i]) ans += i;
  }
  cout << ans << endl;
}