using System;

using System.Collections.Generic;

public class Program

{

    private static int FindPlatform(int[] arrArr, int[] depArr, int n)

    {

        List<int> arr = new List<int>(arrArr);

        List<int> dep = new List<int>(depArr);

        dep.Sort();

        int maxPlatforms = 0;

        int currPlatforms = 0;

        int depIndex = 0;

        int arrIndex = 0;

        while ((depIndex < n) && (arrIndex < n))

        {

            if (arr[arrIndex] <= dep[depIndex])

            {

                Console.WriteLine("arr: " + arr[arrIndex] + " dep: " + dep[depIndex] + " -> adding plaform");

                currPlatforms++;

                maxPlatforms = Math.Max(maxPlatforms, currPlatforms);

                if (arrIndex < n) arrIndex++;// else depIndex++;

            }

            else if (arr[arrIndex] > dep[depIndex])

            {

                Console.WriteLine("arr: " + arr[arrIndex] + " dep: " + dep[depIndex] + " -> removing plaform");

                currPlatforms--;

                if (depIndex < n) depIndex++;// else arrIndex++;

            }

        }

        return maxPlatforms;

    }

    public static void Main()

    {

        int[] arr = new int[] { 900, 940, 950, 1100, 1500, 1800 };

        int[] dep = new int[] { 910, 1200, 1120, 1130, 1900, 2000 };

        int n = 6;

        Console.WriteLine("Minimum Number of Platforms Required = " + FindPlatform(arr, dep, n));

    }

}