Bus_ZadachiNakov

using System;

namespace ConsoleApp210
{
    class Program
    {
        static void Main()
        {
            int passengers = int.Parse(Console.ReadLine());
            int busStops = int.Parse(Console.ReadLine());

            for (int i = 1; i <= busStops; i++)
            {
                int gettingOff = int.Parse(Console.ReadLine());
                int gettingOn = int.Parse(Console.ReadLine());

                if (i % 2 != 0)
                {
                    gettingOn += 2;
                }
                else
                {
                    gettingOff += 2;
                }

                passengers -= gettingOff;//passengers = passengers - gettingOff
                passengers += gettingOn;
            }

            Console.Write(passengers);
        }
    }
}