自然语言对应到map
https://static.cheggcn.com/chegg/653766.html
https://stackoverflow.com/questions/3422673/how-to-evaluate-a-math-expression-given-in-string-form
不要轻易复制粘贴啊啊啊！
变成一位数所需要的次数，加个count就行了
https://www.geeksforgeeks.org/finding-sum-of-digits-of-a-number-until-sum-becomes-single-digit/