1. Precision of 1e-10 seconds is enough to compare boil-time with wake-time.

2. If some guy wakes up at the same time the water is ready (I mean exact equality up to precision), the water is disposed to cups first. So he will fill up an empty tank in this case.

3. Output times after rounding them UP. It is not quite clear from problem statement, but it's the closest guess if we assume that drinking can start only at integer number of seconds. At least this approach gives AC.

4. Output rounded times modulo 24:00:00 (i.e. if cup is ready the next day, subtract 24 from HH).