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MathNet 2018-part-03 — 181 problems (EN–VI) Question 88

Math Olympiad Vault · MathNet 2018-part-03 — 181 problems (EN–VI)

Question 88

The cells of an $8 \times 8$ table are initially white. Alice and Bob play a game. First Alice paints $n$ of the fields in red. Then Bob chooses 4 rows and 4 columns from the table and paints all fields in them in black. Alice wins if there is at least one red field left. Find the least value of $n$ such that Alice can win the game no matter how Bob plays.