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MathNet 2023-part-03 — 191 problems (EN–VI) Question 21

Math Olympiad Vault · MathNet 2023-part-03 — 191 problems (EN–VI)

Question 21

In the fictional country of Mahishmati, there are $50$ cities, including a capital city. Some pairs of cities are connected by two-way flights. Given a city $A$, an ordered list of cities $C_1, \dots, C_{50}$ is called an *antitour* from $A$ if
* every city (including $A$) appears in the list exactly once, and
* for each $k \in \{1, 2, \dots, 50\}$, it is impossible to go from $A$ to $C_k$ by a sequence of exactly $k$ (not necessarily distinct) flights.

Baahubali notices that there is an antitour from $A$ for any city $A$. Further, he can take a sequence of flights, starting from the capital and passing through each city exactly once. Find the least possible total number of antitours from the capital city.