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MathNet 2008-part-04 — 165 problems (EN–VI) Question 113

Math Olympiad Vault · MathNet 2008-part-04 — 165 problems (EN–VI)

Question 113

(Malitskii Yrii) Find out what five-digit numbers are there more: (1) those in which all digits follow from left to right in the order of increasing, or (2) those in which each digit is not greater than $5$ and the order those digits follow from left to right is not descending (e.g. $12459$ satisfies the first condition, while $22589$ and $01234$ don't; $11145$ satisfies the second condition, while $21224$, $12346$, and $01234$ don't).