#include<fstream.h>
#include<math.h>

int main()
{
 ifstream fin("fractii.in");
 ofstream fout("fractii.out");

 int m,n,k,i,j,l,ok,a[1000001];

 fin>>n;
 k=n/2+n%2;
 memset(a,1,2*n);
// for (i=1;i<=n;i++) a[i]=1;
 a[1]=0;
 for (i=2;i<=k;i++)
  if (a[i]) for (j=i*i;j<=n;j+=i) a[j]=0;

 k=2*n-1;
 for (i=2;i<=n;i++)
  for (j=i+1;j<=n;j++)
  {
   ok=2;
   m=sqrt(j)>i?i:j;
   for (l=2;l<=m && ok;l++)
    if (a[l] && !(i%l || j%l))
     ok=0;
   k+=ok;
  }

 fout<<k;

 fin.close();
 fout.close();
 return 0;
}