This problem can be solved by pre-school children in five to ten minutes, by programmers in an hour and by people with higher education… well, check it yourself! What number comes at the question mark?
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Simply count the number of "circles" in the digits of the number. The digit 8 has two circles in its shape so it counts as two, and 0 is one big circle so it counts as 1. As a result, $$2581 = 2$$.
Input
A number $$m \in \mathbb{N}$$.
Output
The number of circles in the digits of $$n$$.Example
Input:
8809Output:
6