I don't know if it's because of blowing on the fan, I got up today and my left leg knee hurts, and after standing for three classes in the afternoon, I went down the stairs to lift one leg, and now as long as I move my knee, it hurts my heart, and I have wiped the medicine and wine, and I am lying on the bed, hoping that it will get better tomorrow, and there are four classes to attend. I'm very sorry, Ruochen is going to take a leave of absence, please forgive me.