Solution.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

class Solution {
        static int getMoneySpent(int[] keyboards, int[] drives, int totalMoneyAvailable)
        {
            var sortedKeyboardPrices = from keyboard in keyboards
                                 orderby keyboard descending
                                 select keyboard;
            var sortedDrivePrices = from drive in drives
                              orderby drive ascending
                              select drive;
            //default if not able to purchase anything
            var maxMoneySpendable = -1;

            foreach (var keyboard in sortedKeyboardPrices)
            {
                foreach (var drive in sortedDrivePrices)
                {
                    if (keyboard + drive <= totalMoneyAvailable)
                    {
                        if (keyboard + drive > maxMoneySpendable)
                            maxMoneySpendable = keyboard + drive;
                    }
                    else
                        break;
                }
            }
            return maxMoneySpendable;
        }

    static void Main(String[] args) {
        string[] tokens_s = Console.ReadLine().Split(' ');
        int s = Convert.ToInt32(tokens_s[0]);
        string[] keyboards_temp = Console.ReadLine().Split(' ');
        int[] keyboards = Array.ConvertAll(keyboards_temp,Int32.Parse);
        string[] drives_temp = Console.ReadLine().Split(' ');
        int[] drives = Array.ConvertAll(drives_temp,Int32.Parse);
        //  The maximum amount of money she can spend on a keyboard and USB drive, or -1 if she can't purchase both items
        int moneySpent = getMoneySpent(keyboards, drives, s);
        Console.WriteLine(moneySpent);
    }
}