var n,m,s:int64;
    i,q:longint;
begin
     assign(input,'sarpe.in');
     reset(input);
     assign(output,'sarpe.out');
     rewrite(output);
     readln(n);
     if n mod 2=1 then q:=1;
     m:=n div 2 +1;
     s:=n*4;
     if n mod 2=1 then
     while n-1>m do
     begin
          dec(n);
          s:=s+n*4;
     end
     else
     while n>m do
     begin
          dec(n);
          s:=s+n*4;
     end;
     if q=1 then s:=s+(n-1)*2;
     writeln(s);
close(output);
end.