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

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] st = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int n = st[0];
            int m = st[1];
            int[] p = new int[2 * m];
            int[] k = new int[2 * m];
            int pi = 0;
            for (int i = 0; i < m; i++)
            {
                st = Console.ReadLine().Split().Select(int.Parse).ToArray();
                p[pi] = st[0];
                k[pi] = 0;
                pi++;
                p[pi] = st[1] + 1;
                k[pi] = 1;
                pi++;
            }
            Array.Sort(p, k);
            int kezd = 0;
            int veg = 0;
            int db = 0;
            for (int i = 0; i < p.Length; i++)
            {
                if (k[i] == 0)
                {
                    kezd++;
                }
                else 
                {
                    veg++;
                }
                if (kezd == veg)
                {
                    db++;
                }
                
            }
            if (p[0] != 1)
            {
                db++;
            }
            else if (p[p.Length - 1] == n + 1)
            {
                db--;
            }
            Console.WriteLine(db);
            Console.ReadKey();


        }
    }
}