program p1;
var i,j,n,s:int64;
    a:array[1..1000000] of int64;
    fi,fo:text;
begin
assign(fi,'fractii.in'); reset(fi);
assign(fo,'fractii.out'); rewrite(fo);

  read(fi,n);
  inc(s);

  for i:=2 to n do
   a[i]:=i-1;

  for i:=2 to n do
   begin
   j:=i*2;
    while j<=n do
     begin
      a[j]:=a[j]-a[i];
      inc(j,i);
     end;
   end;

  for i:=2 to n do
   s:=s+a[i]*2;

  write(fo,s);

close(fi); close(fo);
end.