#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

int main(){
  int k, n;
  vector<int> prime;
  vector<int>::iterator i, j;

  while(cin >> n){
    for(k=2; k<=n; ++k)
      prime.push_back(k);
    
    i = prime.begin();
    while(i != prime.end()){
      j = i + 1;
      while(j != prime.end()){
	if((*j)%(*i) == 0)
	  j = prime.erase(j);
	else
	  ++j;
      }
      ++i;
    }
    cout << prime.size() << endl;
    prime.clear();
  }

  return 0;
}