In mathematics you don't understand things, you just get used to them.

61.P5355 [Ynoi2017]由乃的玉米田由乃在自己的农田边散步,她突然发现田里的一排玉米非常的不美。这排玉米一共有 $N$ 株,它们的高度参差不齐。由乃认为玉米田不美,所以她决定出个数...