#include<fstream.h>
int main ()
{
long n,k=0,i,j;
ifstream f("ciur.in");
ofstream g("ciur.out");
f>>n;
if(n>=2)
{k=1;
for(i=3;i<=n;i=i+2)
 {
 ok=0;
 j=3;
 while(i%j!=0&&j<=i/2)j=j+2;

 if(j>i/2) k++;
 }
}
g<<k;
f.close();
g.close();
return 0;
}