CF131A.cAPS lOCK

wHAT DO WE NEED cAPS LOCK FOR?

Caps lock is a computer keyboard key. Pressing it sets an input mode in which typed letters are capital by default. If it is pressed by accident, it leads to accidents like the one we had in the first passage.

Let's consider that a word has been typed with the Caps lock key accidentally switched on, if:

• either it only contains uppercase letters;
• or all letters except for the first one are uppercase.

In this case we should automatically change the case of all letters. For example, the case of the letters that form words "hELLO", "HTTP", "z" should be changed.

Write a program that applies the rule mentioned above. If the rule cannot be applied, the program should leave the word unchanged.

我们为何需要大写锁定键（Caps Lock）？

Caps Lock 是计算机键盘上的一个按键。按下它后，将进入一种输入模式，在该模式下键入的字母默认为大写。如果误按了该键，就会导致类似第一段中发生的错误。

我们定义：当一个单词在 Caps Lock 键被意外开启的状态下输入时，满足以下任一条件：

• 该单词仅由大写字母组成；
• 该单词除首字母外，其余所有字母均为大写。

此时，我们应自动将该单词中所有字母的大小写进行转换。例如，对于单词 “hELLO”、“HTTP”、“z”，应当改变其中所有字母的大小写。

请编写一个程序，应用上述规则。若该规则不适用于某个单词，则程序应保持该单词不变。

The first line of the input data contains a word consisting of uppercase and lowercase Latin letters. The word's length is from 1 to 100 characters, inclusive.

输入数据的第一行包含一个由大写和小写拉丁字母组成的单词。该单词的长度为 1 到 100 个字符（含端点）。

Print the result of the given word's processing.

输出给定单词处理后的结果。