using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        var input = Console.ReadLine().Split().Select(int.Parse).ToArray();
        var N = input[0];
        var M = input[1];
        var array = new int[N];

        for (int i = 0; i < M; i++)
        {
            var temp = Console.ReadLine().Split().Select(int.Parse).ToArray();
            array[temp[1] - 1] = 1;
        }

        var count = 0;
        foreach (var item in array)
        {
            if (item == 0) count++;
        }

        Console.WriteLine(count);
    }
}