说明：  请编写函fun,函数的功能是：判断字符串是否为回文？或是，函数返回1，主函数中输出：YES,否则返回0，主函数中输出NO。回文诗指顺读和倒读都一样的字符串。 例如，字符串LEVEL是回文，而字符串123312就不是回文。 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。
(Write a letter of fun, function is to: determine whether a string is palindrome? Or, the function returns 1, the main function output: YES, otherwise it returns 0, the main function output NO. Palindrome poem refers to the cis-read and read back the same string. For example, the string is a palindrome LEVEL, and the string 123312 is not a palindrome. 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.)