HackerRank Booking.com - Customer Service Capacity

Program.cs

/*
Problem: Determine how many people need to hire

Input specs:
- first line contains the current number of customer service executives
- second line contains a number of records in data set
- next linkes contains a pair of timestamps representing a start of call and end of call

Input demo:      
1 
3
1481222000 1481222020
1481222000 1481222040
1481222030 1481222035

Expected result (number of additional customer service executives):            
1
*/
static void Main(string[] args)
{
	var executives = int.Parse(Console.ReadLine());
	var n = int.Parse(Console.ReadLine());

	var calls = new List<Call>();
	var concurrent = 0;
	
	for (var i = 0; i < n; i++)
	{
		var timestamps = Console.ReadLine().Split(' ');
		var call = new Call()
		{
			Start = int.Parse(timestamps[0]),
			End = int.Parse(timestamps[1]),
		};

		calls.Add(call);

		var otherCalls = calls.FindAll(x => x.Start >= call.Start || x.End <= call.End); //possible bug here
		if (otherCalls.Count > concurrent)
			concurrent = otherCalls.Count;
	}

	executives = concurrent - executives;

	Console.WriteLine($"Additional executives: {executives}");
	Console.ReadKey();
}

class Call
{
	public int Start { get;  set; }
	public int End { get; set; }
}