#include <iostream>
#include <cstring>
#include <stdio.h>
#include <fstream>
using namespace std;
char v[1000000];
int  main()
{long n,i,d,k,nr,j,p;
 for(i=3;i<=100000;i+=2)
 v[i]=1;
ifstream f("fractii.in");
ofstream g("fractii.out");
 f>>n;
nr=n;


for(i=2;i<=n;i++)
{
 for(j=1;j<=n;j++)
 v[j]=1;
 for(d=2;d<=i/2;d++)
  if(v[d]&& !(i%d))
    for(p=d;p<=n;p+=d)
     v[p]=0;

 for(d=i;d<=n;d++)
   if(v[d]&&!(d%i))
    for(p=d;p<=n;p+=d)
     v[p]=0;

for(j=1;j<=n;j++)
    if(v[j])
    nr++;


}
 g<<nr;


}