This problem is in Contest(s) below:
Contest 1966:计172-1,2,3 -8 函数1
Contest 1967:海162-1,2,3 -9 函数1
Contest 2046:信1702-1C++基础知识(复习回顾)
Contest 2133:信1821-1、2C++基础知识(复习回顾)