#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int N;
ll sum;

int main() {
  cin >> N;
  vector<bool> isprime(N + 1, true);
  for (int i = 2; i * i <= N; i++) {
    if (isprime[i]) {
      for (int j = i * 2; j <= N; j += i) isprime[j] = false;
    }
  }
  for (int i = 2; i <= N; i++) if(isprime[i]) sum += i;
  cout << sum << endl;
  return 0;
}