Calculate a dog’s age in dog’s years

Calculate a dog’s age in dog’s years.
Note:
For the first two years, a dog year is equal to 10.5 human years.
After that, each dog year equals 4 human years.
Expected output:
Input a dog’s age in human years: 15
The dog’s age in dog’s years is 73
h_age = int(input("Input a dog's age in human years: "))

if h_age < 0:
       print("Age must be positive number.")
       exit()
elif h_age <= 2:
       d_age = h_age * 10.5
else:
       d_age = 21 + (h_age - 2) * 4

print("The dog's age in dog's years is", d_age)

Output:

Input a dog's age in human years: 12
The dog's age in dog's years is 61