using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

    class a
    {
        public List<int[][]> combinations(int[][] array1, int count1, int[][] array2, int count2)
        {
            List<int[][]> result= new List<int[][]>();
            combine(array1, count1, array2, count2, new int[4][], out result);
            return result;
        }

    public  void combine(int[][] array1, int count1, int[][] array2, int count2, int[][] chosen, out List<int[][]> result)
    {

       int[][] temp;

        if (count1>0) {
            count1--;
            for (int i = 0; i < array1.GetLength(0) - count1; i++) {
                temp = Concat(chosen,array1); // this copies the array
                combine(array1.WHAT?, count1, array2, count2, temp, result);
            }
        } else if (count2>0) {
            //count2--;
            //for (i = 0; i < array2.length - count2; i++) {
            //    temp = chosen.concat([array2[i]]);
            //    combine(null, 0, array2.slice(i + 1), count2, temp, result);

        } else {
            result.Add(chosen); // don't need to copy here, just accumulate results
        }
    }
        public static T[] Concat<T>(this T[] x, T[] y)
        {
            if (x == null) throw new ArgumentNullException("x");
            if (y == null) throw new ArgumentNullException("y");
            int oldLen = x.Length;
            Array.Resize<T>(ref x, x.Length + y.Length);
            Array.Copy(y, 0, x, oldLen, y.Length);
            return x;
        }

        public static IEnumerable<T> SliceRow<T>(this T[,] array, int row)
        {
            for (var i = 0; i < array.GetLength(0); i++)
            {
                yield return array[i, row];
            }
        }
}