Chaining of comparison operators

Comparison operations in python can be chained together. They can be used to check if a number is within a range, if 3 numbers are not equal to each other, etc.

if 10 <= a <= 20:     # Equivalent to 10 <= a and a <= 20
    print('variable is in [10; 20] range')
    print('Great!')
if a != b != c:       # Equivalent to a != b and b != c
    print('b is different from both a and c')

Challenge

Given the age of a person, we would like to know what would be their stage of life:

Input is given as a single integer number. Print the stage of life of that person.