string check;
    for (int row = 0; row < LIMIT; row++)
    {
        for (int column = 0; column < LIMIT; column++)
        {
            if (check.find(matrix[row][column], 0) == -1) // fant ikke tallet, da legger vi det til i strengen
                check += matrix[row][column];
            else
                cout << "Found duplicate in row " << row + 1 << ", column " << column + 1 << ".\n";
        }
    }