/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		List<List<Integer>> adj =  new ArrayList<>(n);
		
		for(int i=0;i<=n;i++){
			adj.add(new ArrayList<>());
		}
		System.out.println(adj);
		for(int i=0;i<m;i++){
			int u=sc.nextInt();
			int v = sc.nextInt();
			adj.get(u).add(v);
			adj.get(v).add(u);
			
		}
		bfs(adj,1);
	}
	public static void bfs(List<List<Integer>> adj,int src){
		List<Integer> ans = new ArrayList<>();
		Queue<Integer> q = new LinkedList<>();
		boolean visited[] = new boolean[adj.size()];
		int level[] = new int[adj.size()];
		q.add(src);
		visited[src] = true;
		level[src] = 0;
		
		while(!q.isEmpty()){
			int cur = q.poll();
			ans.add(cur);
			
			for(int x : adj.get(cur)){
				if(!visited[x]){
					visited[x] = true;
					q.add(x);
					level[x] = level[cur]+1;
				}
			}
		}
		
		System.out.println(ans);
		System.out.println("Level -->"+Arrays.toString(level));
	}
}