#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n,phi[1000005];
long long sol;
int main()
{ int i,j;
    f>>n;
   for(i=2;i<=n;i++)
      phi[i]=i-1;

   for(i=2;i<=n;i++)
    { sol+=phi[i];
    for(j=i+i;j<=n;j+=i)
      phi[j]-=phi[i];
    }
   g<<2*sol+1;
    return 0;
}