Given a time in -hour AM/PM format, convert it to military (24-hour) time.
Note: - 12:00:00AM on a 12-hour clock is 00:00:00 on a 24-hour clock.
- 12:00:00PM on a 12-hour clock is 12:00:00 on a 24-hour clock.
Example
Return '12:01:00'.
Return '00:01:00'.
