var i,j,n:longint;
    sum:int64;
    ph:array[1..1000000] of longint;

begin
     assign(input,'fractii.in'); reset(input);
     read(input,n); close(input);
     for i:=1 to n do ph[i]:=i-1;
     for i:=2 to n do
     begin
     j:=2*i;
      while j<=n do
       begin
             ph[j]:=ph[j]-ph[i];
             j:=j+i;
       end;
     end;
   sum:=1;
   for i:=1 to n do sum:=sum+(2*ph[i]);
   assign(output,'fractii.out'); rewrite(output);
   write(output,sum); close(output);

end.