program eratostene;
 var a:array[1..1000000]of longint;
     n,i,j,s:longint;
     f:text;
 begin
  assign(f,'fractii.in');
  reset(f);
  readln(f,n);
  close(f);
  a[1]:=n;
  for i:=2 to n do
   a[i]:=n-1;
  i:=2;
  while i<=n div 2 do
   begin
    if a[i]=n-1 then
      for j:=1 to n div i do
        a[i*j]:=a[i*j]-n div i+1;
    inc(i)
   end;
  for i:=1 to n do
   s:=s+a[i];
  assign(f,'fractii.out');
  rewrite(f);
  writeln(f,s);
  close(f);
 end.