# $10\times10$ table of numbers with differences of adjacent entries no more than 5

In each square in a table $10\times 10$ we write a whole number so the difference between any two numbers by the neighboring squares must be no more than $5$ (two squares are neighboring if they have a common side). Show that two of the numbers must be equal. Please help me!

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What have you tried? –  Matthew Pressland Feb 28 '13 at 18:33

Done. ${}{}{}{}{}{}{}$ –  Joe Z. Feb 28 '13 at 21:21