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Problem 399

Number theory Difficulty 2.6 Find the answer Junior Mathematical Olympiad, September · Netherlands · 2019

We compute the square of each of the numbers from $1$ to $2019$ . We take the last digit from each of the resulting squares, and then we add those $2019$ digits together.
What number do we get?

Your answer

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Official solution

9090

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