#include <fstream>

using namespace std;

ifstream fi("ciur.in");
ofstream fo("ciur.out");

int n, i, j, a[2000000], c;

int main()
{
    fi>> n;
    for(i=1;i<=n;i++)
    a[i]=i;
    for(i=2;i<=n;i++)
      if(a[i]!=0)
      {
          c++;
      for(j=i;j<=n;j++)
        if(a[j]!=0)
        if(a[j]%i==0)
        a[j]=0;}
        fo<<c;
}