#include <iostream>
#include <fstream>

long long x[2000000];

using namespace std;

int main()
{
  int n,i,k,rez=-1;

  ifstream ciurin("ciur.in");
  ofstream ciurout("ciur.out");

  ciurin>>n;

  for (i=1;i<=n;++i)
    x[i]=i;

  for (i=2;i<=n;++i)
    for (k=2;k<=n;++k)
      if (x[k]%i==0 && x[k]!=i)
        x[k]=0;

  for (i=1;i<=n;++i)
    if (x[i]!=0)
      ++rez;
  ciurout<<rez;

    return 0;
}