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

bool isp(int n) {
  if (n < 2) return false;
  else if (n == 2) return true;
  else if (n % 2 == 0) return false;
  double d = sqrt(n);
  for (int i = 3; i <= d; i += 2) if (n % i == 0) return false;
  return true;
}

int main() {
  int N;
  cin >> N;
  int sum = 0;
  for (int i = 2; i <= N; i++) if (isp(i)) sum += i;
  cout << sum << "\n";
}