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

using System.Data;

namespace ConsoleApp51
{
    class Program
    {
        static int target = 0;
        static void Main(string[] args)
        {
            List<int> nums = new List<int>() { 1, 2, 3, 4, 5, 6 };
            target = 999;

            generate(nums, 2);
            generate(nums, 3);
            generate(nums, 4);
            generate(nums, 5);
            generate(nums, 6);
        }

        static List<string> list1 = new List<string>();
        static List<string> list2 = new List<string>();
        static List<string> list3 = new List<string>();
        static List<string> list4 = new List<string>();
        static List<string> list5 = new List<string>();
        static List<string> list6 = new List<string>();
        private static void generate(List<int> nums, int l)
        {
            for (int i = 0; i < nums.Count; i++)
            {
                for (int j = i + 1; j < nums.Count; j++)
                {
                    if (l == 2)
                    {
                        list1.Clear();
                        list1.Add(nums[i].ToString());
                        list1.Add(nums[j].ToString());

                        list2.Add(add(list1));

                        list2.Add(sub(list1)[0]);
                        list2.Add(sub(list1)[1]);

                        list2.Add(mul(list1));

                        list2.Add(div(list1)[0]);
                        list2.Add(div(list1)[1]);
                    }
                    else if (l == 3)
                    {
                        addToList(list2, list3, nums);
                    }
                    else if (l == 4)
                    {
                        addToList(list3, list4, nums);
                    }
                    else if (l == 5)
                    {
                        addToList(list4, list5, nums);
                    }
                    else if (l == 6)
                    {
                        addToList(list5, list6, nums);
                    }
                }
            }
        }

        private static string add(List<string> list)
        {
            return "(" + list[0] + "+" + list[1] + ")";
        }
        private static List<string> sub(List<string> list)
        {
            List<string> subList = new List<string>();

            subList.Add("(" + list[0] + "-" + list[1] + ")");
            subList.Add("(" + list[1] + "-" + list[0] + ")");

            return subList;
        }
        private static string mul(List<string> list)
        {
            return "(" + list[0] + "*" + list[1] + ")";
        }
        private static List<string> div(List<string> list)
        {
            List<string> divList = new List<string>();

            divList.Add("(" + list[0] + "/" + list[1] + ")");
            divList.Add("(" + list[1] + "/" + list[0] + ")");

            return divList;
        }
        private static void addToList(List<string> lista1, List<string> lista2, List<int> nums)
        {
            List<string> lista3 = new List<string>();
            foreach (string x in lista1)
            {
                for (int k = 0; k < nums.Count; k++)
                {
                    if (x.Contains(nums[k].ToString()))
                    {
                        continue;
                    }
                    else
                    {
                        lista3.Clear();
                        lista3.Add(nums[k].ToString());
                        lista3.Add(x);

                        lista2.Add(add(lista3));

                        lista2.Add(sub(lista3)[0]);
                        lista2.Add(sub(lista3)[1]);

                        lista2.Add(mul(lista3));

                        lista2.Add(div(lista3)[0]);
                        lista2.Add(div(lista3)[1]);
                    }
                }
            }
        }
    }
}