var phi:array[2..1000000] of longint;
    f,g:text;
    i,j,n:longint;
    sum:int64;
begin
 assign(f,'fractii.in'); reset(f);
 assign(g,'fractii.out'); rewrite(g);
 read(f,n);
 for i:=2 to n do
  phi[i]:=i;
 j:=2;
 while (j<=n) do begin
  phi[j]:=phi[j] shr 1;
  j:=j+2;
 end;
 for i:=3 to n do
  if phi[i]=i then begin
   j:=i;
   while (j<=n) do begin
    phi[j]:=phi[j]-(phi[j] div i);
    j:=j+i;
   end;
  end;
 sum:=0;
 for i:=2 to n do
  sum:=sum+phi[i];
 sum:=sum shl 1+1;
 writeln(g,sum);
 close(f); close(g);
end.