#include<iostream>
#include<deque>
#include<algorithm>
#include<vector>
#include<fstream>
using namespace std;

ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");

struct edge{
	int a,b;
	bool visited;
};

int n,m;
vector<vector<int>> g;
vector<edge> edges;
vector<int> result;

void read(){
	in>>n>>m;
	g.resize(n+1);
	edges.resize(m);
	int a,b;
	for(int i=0;i<m;i++){
		in>>a>>b;
		edges[i] = {a,b,false};

		g[a].push_back(i);
		g[b].push_back(i);
	}
}

void euler(int node){
	for(int k:g[node]){
		if(edges[k].visited){
			continue;
		}
		edges[k].visited = true;
		int next = (node == edges[k].a) ? edges[k].b : edges[k].a;
		euler(next);
	}
	result.push_back(node);
}

void solve(){
	for(int i=1;i<=n;i++){
		if(g[i].size()%2==1){
			out<<-1;
			return;
		}
	}
	euler(1);
	result.pop_back();
	for(int k:result){
		out<<k<<" ";
	}
}


int main(){
	read();
	solve();

	return 0;
}