一个C程序，其想要输出20个减号，不过，粗心的程序员把代码写错了，你需要把下面的代码修改正确，不过，你只能增加或是修改其中的一个字符，给出三种答案。-A C program, its desired output of 20 minus sign, but the careless programmer to code wrong, you need to modify the following code is correct, but you can only add or modify one of the characters, given three kinds of answers.