题目内容：

enum用法实例C++
帮忙写一个.
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Key in a time of hour randomly,print good morning/noon/afternoon/evening/night respectively.
Requirement:use Enumeration constant.
Note that the roughly partition of a day is as follow:
1)Morning:The first or early part of the day,lasting from midnight to noon or from sunrise to noon.Six o'clock could be the start of the interval.
2)Noon:Twelve o'clock in the daytime; midday.
3)Afternoon:The part of day from noon until sunset.Say,after 13 o’clock.
4)Evening:The period of decreasing daylight between afternoon and night,after eighteen o’clock.
5)Night:The period between sunset and sunrise,especially the hours of darkness.To ensure the whole day and night are included,we suggest that it begin at 21 o’clock.
I/O Examples:
8
good morning.
12
good noon.
17
good afternoon.
19
good evening.
22
good night.
-1
the input is invalid.
Note that the input/output must follow the above format.