Bus

using System;

namespace Bus
{
    class Program
    {
        static void Main(string[] args)
        {
            int passengers = int.Parse(Console.ReadLine());
            int stations = int.Parse(Console.ReadLine());

            for (int i = 1; i <= stations; i++)
            {
                int outputPassengers = int.Parse(Console.ReadLine());
                int inputPassengers = int.Parse(Console.ReadLine());

                passengers += inputPassengers - outputPassengers;

                if (i % 2 == 1)
                {
                    passengers += 2;
                }
                else
                {
                    passengers -= 2;
                }
            }

            Console.WriteLine($"The final number of passengers is : {passengers}");
        }
    }
}