Dog years

We think that one dog year is equal to 7 human years. That's not true, on average the first dog year is equal to 15 human years, the second dog year is equal to 9 human years, from the third to the sixth each is equal 4 human years and every next year after that is equal to 5 human years.

If you know how old is your dog in dog years, calculate how old it is human years.

Write a function named dogYears that given a natural number N from input representing the years of your dog. Return how old is your dog in human years.

Input
2

Output
24

Input
4

Output
32

Explanation #1: 2 dog years are equal to 15 + 9 = 24 human years
Explanation #2: 4 dog years are equal to 15 + 9 + 4 + 4 = 32 human years