Latin square

A Latin square of $n$ is an $n\\times n$ array such that each column and each row are made with the same $n$ symbols, using every one exactly once .

Examples.

\\left(\\begin{array}[]{cccc}a&b&c&d\\\\c&d&a&b\\\\d&c&b&a\\\\b&a&d&c\\end{array}\\right)\\qquad\\left(\\begin{array}[]{cccc}1&2&3&4\\\\4&3&2&1\\\\2&1&4&3\\\\3&4&1&2\\end{array}\\right)

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