function checkdigit(n)
    matrix = (
        (0, 3, 1, 7, 5, 9, 8, 6, 4, 2),
        (7, 0, 9, 2, 1, 5, 4, 8, 6, 3),
        (4, 2, 0, 6, 8, 7, 1, 3, 5, 9),
        (1, 7, 5, 0, 9, 8, 3, 4, 2, 6),
        (6, 1, 2, 3, 0, 4, 5, 9, 7, 8),
        (3, 6, 7, 4, 2, 0, 9, 5, 8, 1),
        (5, 8, 6, 9, 7, 2, 0, 1, 3, 4),
        (8, 9, 4, 5, 3, 6, 2, 0, 1, 7),
        (9, 4, 3, 8, 6, 1, 7, 2, 0, 5),
        (2, 5, 8, 1, 4, 3, 6, 7, 9, 0))
    row = 0
    for d in string(n)
        row = matrix[row + 1][d - '0' + 1]
    end
    return row
end

foreach(i -> println("$i validates as: ", checkdigit(string(i)) == 0), [5724, 5727, 112946])