输入一个字符串，将其中大写字母转换为对应小写字母之后的第五个字母，若原始大写字母为V～Z, 则转换为对应小写字母的值减21。其他字符不变，输出转换后的字符串。 例如，对于字母A，则转换为小写字母f；若形参是字母W，则转换为小写字母b。-Enter a string, which will be converted to uppercase lowercase letter in the fifth after, if the original capital letter V ~ Z, then converted to a value corresponding to the minus 21 lowercase letters. Other characters unchanged, string output after conversion. For example, the letter A, then converted to lowercase f　if the parameter is the letter W, then converted to lowercase b.