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

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

int main(){
  int n; cin >> n;
  vector<bool> prime = Eratosthenes(n);
  int ans = 0;
  for (int i = 1; i <= n; i++) {
    if (prime[i]) ans += i;
  }
  cout << ans << endl;
  return 0;
}