[计] delete before current position

shān chú dāng qián wèi zhì yǐ qián de nèi róng ㄕㄢ ㄔㄨˊ ㄉㄤ ㄑㄧㄢˊ ㄨㄟˋ ㄓˋ ㄧˇ ㄑㄧㄢˊ ㄉㄜ˙ ㄋㄟˋ ㄖㄨㄥˊ