#include <iostream>
#include <fstream>
using namespace std;
int main()
{
 long a[2000000],n,i,j,nr,x;
 ifstream f("ciur.in");
 ofstream g("ciur.out");
 f>>n;
 for(i=2;i<=n;i++)
   a[i]=i;
nr=1;
i=2;
while(i<=n)
  {
      x=i;
      for(j=i;j<=n;j++)
        if(a[j]%i==0)
          a[j]=-1;
      for(j=i;j<=n;j++)
         if(a[j]!=-1)
           {
            i=a[j];
            nr++;
            j=n+1;
           }
    if(x==i)
      i=n+1;
  }
  g<<nr;
  f.close();
  g.close();
return 0;
}