var     s:int64;
        i,j,n:longint;
        f:text;
        a:array [0..1000000] of boolean;
        v:array [1..1000000] of longint;

begin
  assign(f,'fractii.in');
  reset(f);
  readln(f,n);
  close(f);

  for i:=1 to n do
    begin
      a[i]:=true;
      v[i]:=i;
    end;

  for i:=2 to n do
    if a[i] then
      begin
        j:=i;
        while j<=n do
          begin
            a[j]:=false;
            v[j]:=v[j]*(i-1) div i;
            inc(j,i);
          end;
      end;

  s:=1;
  for i:=2 to n do
    s:=s+2*v[i];

  assign(f,'fractii.out');
  rewrite(f);
  writeln(f,s);
  close(f);
end.