Question 1132815
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The problem sounds as if it might be interesting; but the statement of the problem is not clear.<br>
You say 300 and 2018 are not Rustam's numbers; but 30 is a 2-digit multiple of 5, and 10, 20, and 80 are all 2-digit multiples of 5.<br>
There is no point in our trying to count the number of Rustam's numbers if we don't have a clear definition of what they are.