N名学生的成绩已在主函数中放入一个带头节点的链表结构中，h指向链表的头节点。请编写函数fun，它的功能是：求出平均分，由函数值返回。

例如，若学生的成绩是：85，76，69，85，91，72，64，87，则平均分应当是：78.625.

注意：部分源程序在文件PROG1.C中。

请勿改动主函数main和其它函数中的任何内容，仅在函数fun的花括号中填入你编写的若干语句。

-N student achievement has been the main function into a linked list structure to take the lead node, h point to the head of the list node. Please write the function fun, it' s function is to: find the average, the value returned by the function. For example, if student achievement is: 85,76,69,85,91,72,64,87, the average should be: 78.625. Note: Some source code in the file PROG1.C. Do not change main function and other functions in any content, only the braces in the function fun fill a number of statements you write.