/* -*- coding: utf-8 -*-
 *
 * 713.cc: No.713 素数の和 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_P = 1000;

/* typedef */

/* global variables */

bool primes[MAX_P + 1];

/* subroutines */

int gen_primes(int maxp) {
  memset(primes, true, sizeof(primes));
  primes[0] = primes[1] = false;

  int p, sum = 0;
  for (p = 2; p * p <= maxp; p++)
    if (primes[p]) {
      sum += p;
      for (int q = p * p; q <= maxp; q += p) primes[q] = false;
    }

  for (; p <= maxp; p++)
    if (primes[p]) sum += p;

  return sum;
}

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  int sum = gen_primes(n);
  printf("%d\n", sum);
  return 0;
}