Problem 7. Truck Tour - my variant

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

namespace Stacks
{
    class Program
    {
        static void Main(string[] args)
        {
            long countOfPumps = long.Parse(Console.ReadLine());

            Queue<long> pumps = new Queue<long>();

            for (int i = 0; i < countOfPumps; i++)
            {
                var data = Console.ReadLine()
                    .Split()
                    .Select(long.Parse)
                    .ToArray();

                long num1 = data[0];
                long num2 = data[1];
                pumps.Enqueue(num1);
                pumps.Enqueue(num2);
            }

            long leftFuel = 0;
            int index = 0;
            int counter = 0;
            int mainCounter = 0;

            while (true)
            {
                var liters = pumps.Dequeue();
                var distance = pumps.Dequeue();

                if (liters + leftFuel >= distance)
                {
                    leftFuel = leftFuel + liters - distance;
                    counter++;
                }
                else if (liters + leftFuel < distance)
                {
                    index = mainCounter + 1;
                    counter = 0;
                }

                pumps.Enqueue(liters);
                pumps.Enqueue(distance);

                if (counter >= countOfPumps)
                {
                    Console.WriteLine(index);
                    return;
                }
                mainCounter++;
            }
        }
    }
}