请编写函数fun,函数的功能是：统计一行字符串中单词的个数，作为函数值返回。一行字符串在主函数中输入，规定所有单词由小写字母组成，单词中间由若干个空格隔开，一行的开始没有空格。-Please write a function fun, function is the function: Counts the number of his string of words, as a function of the value returned. His string entered in the main function, the provisions of all the words lowercase letters, words separated by a number of spaces, beginning of the line with no spaces.