#include<fstream.h>
#define N 1000001
long n,i,k,x[N];
long long r=1;
int main()
{ifstream f("fractii.in");
ofstream g("fractii.out");
f>>n;
for(i=1;i<=n;i++)
       x[i]=i;       
for(i=1;i<=n;i++)
       {for(k=i+i;k<=n;k+=i)
               x[k]-=x[i];}
for(i=2;i<=n;i++)
       r=r+2*x[i];
g<<r;
f.close();
g.close();
return 0;}