In a computer game, each gamer has an army of units.
Write a program that will classify the army of your enemies corresponding to the following rules:
Units: Category
less than 1: no army
from 1 to 9: few
from 10 to 49: pack
from 50 to 499: horde
from 500 to 999: swarm
1000 and more: legion
The program should read the number of units and output the corresponding category.
