Need help with C++ Loops Exercise

Из книги Кея Хорстманна «C ++ для всех» Chapter 4: Loops

Write a program that adds up the sum of all odd digits of n. (For example, if n is 32677, the sum would be 3 + 7 + 7 = 17)

I don't know how to make the computer "see" the numbers like separate them