program suma;
const fin = 'fractii.in';
      fout = 'fractii.out';
var c,i,j,n:longint;
    sol:int64;
    t:array [1..1000000] of longint;
begin
  {citire}
  assign(input,fin);
  assign(output,fout);
  reset(input);
  rewrite(output);
  read(n);
  for i:=1 to n do
    t[i]:=i-1;
  for i:= 2 to n do
  begin
    j:=2*i;
    while j<=n do
    begin
      dec(t[j],t[i]);
      inc(j,i);
    end;
  end;
  sol:=1;
  for i:=2 to n do
    sol:=sol+2*t[i];
  {tipar}
  write(sol);
  close(input);
  close(output);
end.