#include <bits/stdc++.h>

using namespace std;

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

int main() {
  int N;
  scanf("%d", &N);
  vector<bool> is_prime = sieve(N + 1);

  int ans = 0;
  for (int i = 2; i <= N; ++i) {
    if (is_prime[i]) ans += i;
  }
  printf("%d\n", ans);
  return 0;
}