Last episode background music

Hi guys, Is there anyone know what is the background music was playing in the last episode (episode 24, not the extra episode)? On the last minute when Zhou Si Yue takes Ding Xian's hand, then she looks back to her younger self back to high school and smile. I was moved by that scene, it seems to me like Ding Xian finally got what she deserved and happiness at last. Now that music keeps playing on my head. I really appreciate if you have any idea, I have tried to search by many ways like in Chinese but no hope. Thank you!