MathForces: Math Olympiads
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Author: mathforces
Problem has been solved: 9 times

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There are $ x $ cities in country $ X $ numbered from 1 to $ x $, some of which have one-way flights, each of which belongs to one of two airlines $ A $ and $ B $. There is a direct flight from the city $ i $ to the city $ j $ if and only if $ i < j $. Find the smallest value of $ x $ such that for any distribution of flights between two airlines, you can fly a path from 2019 cities using flights of only one of the airlines.

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