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MathNet 2025-part-01 — 187 problems (EN–VI) Question 100

Math Olympiad Vault · MathNet 2025-part-01 — 187 problems (EN–VI)

Question 100

The JMO Cluster initially consists of five stars $O$, $A$, $B$, $C$, and $D$. Each star is assigned a value called its **importance**. The importance of $O$ is $0$, and the importance of each of $A$, $B$, $C$, and $D$ is $1$. Moreover, there are one-way direct flights from $O$ to $A$ and $C$; from $A$ to $B$ and $D$; from $B$ to $O$; from $C$ to $B$ and $D$; and from $D$ to $O$, and no other direct flights exist.
To prevent the stars from aging, the JMO Cluster periodically performs an operation consisting of the following sequence of actions:
(1) Abolish all existing direct flights and destroy all the stars.
(2) For each direct flight $f$ abolished in step (1), construct a new star $S_f$. Then assign to $S_f$ an importance equal to the sum of the importances of the departure and arrival stars of $f$.
(3) For every ordered pair $(f, f')$ of two abolished direct flights such that the arrival star of $f$ coincides with the departure star of $f'$, open a one-way direct flight from $S_f$ to $S_{f'}$.
Find the sum of the importances of the stars constructed in the 100th operation.
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