import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		int[] c = new int[n];
		for (int i = 0; i < m; i++) {
			sc.nextInt();
			int b = sc.nextInt() - 1;
			c[b]++;
		}
		sc.close();

		int ans = 0;
		for (int i = 0; i < c.length; i++) {
			if (c[i] == 0) {
				ans++;
			}
		}
		System.out.println(ans);
	}
}