bus

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Problem5
{
    class Program
    {
        static void Main(string[] args)
        {
            int numberOfPeople = int.Parse(Console.ReadLine());
            int numberOfStops = int.Parse(Console.ReadLine()); //for

            for (int counterOfStops = 1; counterOfStops <= numberOfStops; counterOfStops++)
            {
                int peopleOutBus = int.Parse(Console.ReadLine());
                int peopleInBus = int.Parse(Console.ReadLine());

                if(counterOfStops % 2 != 0)
                {
                    numberOfPeople = (numberOfPeople - peopleOutBus) + (peopleInBus + 2);
                }
                else
                {
                    numberOfPeople = (numberOfPeople - peopleOutBus - 2) + peopleInBus;
                }
            }

            Console.WriteLine("The final number of passengers is : {0}", numberOfPeople);
        }
    }
}