# Distinct Digits Function

Algebra Level pending

The function $$\text{dd}(n)$$ takes in a positive integer $$n$$, and gives the number of distinct digits in $$n$$, when written in base 10.

How many elements are there in the range of $$\text{dd}(n)$$?

As an explicit example, $$\text{dd}(1123) = 3$$, since there are three distinct digits in 1123, namely 1, 2, and 3.

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