Given a non-negative integer, count how many of its digits are 3. Here are some suggestions for this and several other problems where you have to process all the digits of a number. Suggestion #1: You can look at the last digit of a number using num % 10 Suggestion #2: You can cut off the last digit of a number by assigning num = num / 10 Suggestion #3: As long as num is still positive, you know there are still digits left in it that need to be processed.