#include <fstream>
#include <valarray>
using namespace std;
long j,a,i,n;
bool v[2000001];
int main()
{
   
   ifstream f("ciur.in");
   ofstream g("ciur.out");
   f>>n;
   for (i=2;i<=n;i+=2)
    v[i]=true; 
   for (i=3;i<=n;i+=2)
    if (!v[i])
    {
     a++;         
     for (j=i+i;j<=n;j+=i)
      v[j]=true;
    }  
   g<<a+1;
   f.close();
   g.close();
   return 0;

}