#include<fstream.h>
int ok[10000];
int main()
{unsigned long n,i,j,k=0;

ifstream f("ciur.in");
ofstream g("ciur.out");

f>>n;

for(i=2;i<=n;i++)
   if(ok[i]==0)
     {j=2;k++;
      while(i*j<=n){ok[i*j]=1;
		    j++;
		    }
      }
     

g<<k<<'\n';

f.close();
g.close();
return 0;
}