package graphs;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Scanner;

public class Euler {
	
	protected class Edge {
		
		private int u;
		private int v;
		private boolean used;

		protected Edge(int u, int v) {
			this.u = u;
			this.v = v;
			used = false;
		}
		
		protected void use() {
			this.used = true;
		}
		
		protected boolean isUsed() {
			return used;
		}
		
		protected int getU() {
			return u;
		}
		
		protected int getV() {
			return v;
		}
	}
	
	private Scanner sc;
	private PrintWriter pw;

	private static ArrayList<Integer>[] graph;
	private static ArrayList<Edge> edges; 
	private static ArrayList<Integer> solution;
		
	public Euler() throws FileNotFoundException {
		
		edges = new ArrayList<Edge>();
		solution = new ArrayList<Integer>();
		pw = new PrintWriter(new File("ciclueuluer.out"));
		
		readData();
				
		parseGraph(0);
		
		if (solution.size() == edges.size()) {
			for(int v : solution) {
				pw.print((v + 1) + " ");
			}
		} else {
			pw.println("-1");
		}
		
		pw.close();
	}
	
	@SuppressWarnings("unchecked")
	private void readData() {
		try {
			sc = new Scanner(new File("ciclueuluer.in"));
			
			graph = new ArrayList[sc.nextInt()];
			
			int vertexs = sc.nextInt();
			
			for (int i = 0; i < vertexs; i++) {
				int vertex1 = sc.nextInt() - 1;
				int vertex2 = sc.nextInt() - 1;
				
				if (graph[vertex1] == null) {
					graph[vertex1] = new ArrayList<Integer>();
				}
				if (graph[vertex2] == null) {
					graph[vertex2] = new ArrayList<Integer>();
				}
				
				edges.add(new Edge(vertex1, vertex2));
				
				if (!graph[vertex1].contains(vertex2)) {
					graph[vertex1].add(vertex2);
				}
				
				if (!graph[vertex2].contains(vertex1)) {
					graph[vertex2].add(vertex1);
				}
			}
				
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} finally {
			sc.close();
		}
	}
	
	
	public static Edge returnEdge(int u, int v) {
		for(Edge edge : edges) {
			if (edge.getU() == u && edge.getV() == v) {
				return edge;
			}
		}
		return null;
	}
	
	
	private static void parseGraph(int vertex) {	
		
		solution.add(vertex);
		
		for(int adj : graph[vertex]) {
			Edge edge = returnEdge(vertex, adj);
			if (edge != null && !edge.isUsed()) {
				edge.use();
				parseGraph(adj);
			}
		}
		
	}
	
	
	public static void main(String args[]) {
		try {
			new Euler();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
	}

}