#include <iostream>
#include <cmath>

#define MAX 100000

using namespace std;

bool prime[MAX+1];
int T[MAX];

void eratos(int n) {
  for(int i = 0; i < n; i++) prime[i] = false;
  for(int i = 3; i <=n; i+=2)prime[i] = true;
  prime[2] = true;
  for(int i = 3, limit = (int)sqrt(n); i <= limit; i += 2) {
    if(!prime[i]) continue;
    for(int j = i*i, k = i*2; j <= n; j += k) prime[j] = false;
  }
}

void init() {
  eratos(MAX);

  for(int i = 0; i < MAX; i++) {
    T[i] = T[i-1];
    if(prime[i]) T[i]++;
  }
}

main() {
  init();
  int n;
  
  while(cin >> n) cout << T[n] << endl;
}