var i,j,n:longint;
v:array[1..1000000] of longint;
f,g:text;
nr:int64;

procedure deschidere;
begin
assign(f,'fractii.in');
assign(g,'fractii.out');
reset(f);
rewrite(g);
end;

procedure a;
begin
  readln(f,n);
  nr:=1;
  for i:=1 to n do
    v[i]:=i-1;
  for i:=2 to n do
    begin
      j:=i*2;
      while (j<=n) do
        begin
          v[j]:=v[j]-v[i];
          j:=j+i;
        end;
      nr:=nr+2*v[i];
    end;
write(g,nr);
end;

begin
  deschidere;
  a;
  close(f);
  close(g);
end.