P65Ex13

        public static void AppearOnce(int[,] m)
        {
            int[] arr = new int[m.Length];
            int count = 0, countApp = 0, k = 0, j = 0, row = 0, col = 0;
            while (j < m.GetLength(1))
            {
                countApp = row = col = 0;
                while (col < m.GetLength(1))
                {
                    if (m[row, col] == m[j, k] && !(row == j && col == k))
                        countApp++;
                    row++;
                    if (row == m.GetLength(0))
                    {
                        row = 0;
                        col++;
                    }
                }
                if (countApp == 0)
                {
                    arr[count] = m[j, k];
                    count++;
                }
                k++;
                if (k == m.GetLength(0))
                {
                    k = 0;
                    j++;
                }
            }
            for (int i = 0; i < count; i++)
                Console.Write(arr[i]);
            Console.WriteLine();
        }