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MathNet 2017-part-03 — 176 problems (EN–VI) Question 42

Math Olympiad Vault · MathNet 2017-part-03 — 176 problems (EN–VI)

Question 42

In the blackboard are written some positive integers. We define the following movements:

(α) Every two successive numbers, say $n, n+1$, can be deleted by writing the number $n-2$.

(β) Every two numbers having difference 4, say $k, k+4$, can be deleted by writing the number $k-1$.

In the case we cannot apply any of the above movements the process finishes.

Determine the maximal possible value of the integer $c$ with the following property: Irrespectively with the numbers are written at the beginning in the table, at all process, all the numbers written in the table are greater than or equal to $c$.