var a:array[1..1000000]of longint;
    b:array[1..1000000]of boolean;
    i,j,n:longint; k:int64; f:text;
begin
 assign(f,'fractii.in');
 reset(f);
 readln(f,n);
 close(f);
 for i:=1 to n do begin a[i]:=i; b[i]:=true; end;
 for i:=2 to n do
  if b[i] then
   begin
    j:=i;
    while j<=n do
     begin
      b[j]:=false;
      a[j]:=a[j]div i * (i-1);
      j:=j+i;
     end;
   end;
 k:=1;
 for i:=2 to n do k:=k+2*a[i];
 assign(f,'fractii.out');
 rewrite(f);
 writeln(f,k);
 close(f);
end.