using static System.Math;
using System.Collections.Generic;
using System.Linq;
using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var m = int.Parse(line[1]);
        getAns(n,m);
    }
    static void getAns(int n, int m)
    {
        var from = new bool[n];
        for (int i = 0; i < m; i++)
        {
            string[] line = Console.ReadLine().Trim().Split(' ');
            var w = int.Parse(line[1]) - 1;
            from[w] = true;
        }
        var ans = from.Count(x => x == false);
        Console.WriteLine(ans);
    }
}