#include <iostream>
using namespace std;

int a[1000000];

int main()
{
  int n;
  int count;

  for (int i = 2; i < 1000000; i++){
    a[i] = 1;
  }

  for (int i = 0; i * i < 1000000; i++){
    if  (a[i] == 1){
      for (int j = 2; j * i <= 100000; j++){
        a[j * i] = 0;
      }
    }
  }

  while (cin >> n){
    count = 0;
    for (int i = 0; i < 1000000; i++){
      if (a[i] == 1){
        count++;
      }
    }
  }

  cout << count << endl;

  return (1);
}