#include <fstream>
using namespace std;
ifstream in ("ciur.in");
ofstream out ("ciur.out");
bool v[200000001];
int main()
{
   int n,i,j,gigel=0;
   in>>n;
   v[1]=1;
   v[2]=0;
   for(i=2;i*i<=n;i++)
if(v[i]==0)
    for(j=i;j*i<=n;j++)
   {
       v[i*j]=1;
   }
   for(i=1;i<=n;i++)
   {
       if(v[i]==0)
        gigel++;
   }
   out<<gigel;
    return 0;
}