import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int M = sc.nextInt();
		boolean[][] arr = new boolean[N+1][N+1];
		LinkedList<Integer> freind = new LinkedList<>();
		for(int i=0; i<M; i++) {
			int a = sc.nextInt();
			int b = sc.nextInt();
			
			arr[a][b] = true;
			arr[b][a] = true;
		}
		
		for(int i=1; i<=N; i++) {
			if(arr[1][i]) {
				freind.add(i);
				
				for(int j=1; j<=N; j++) {
					if(arr[i][j])
						freind.add(j);
				}
			}
		}
		
		//중복제거
		LinkedList<Integer> ans = new LinkedList<>();
		for(int i=0; i<freind.size(); i++) {
			int num = freind.get(i);
			if(!ans.contains(num)) {
				if(num!=1)
					ans.add(num);
			}
		}
		System.out.println(ans.size());
	}
}