// http://infoarena.ro/problema/ciclueuler
#include <fstream>
#include <list>
using namespace std;

int nodes,edges;
list<int> graph[100001];
list<int> solution;

void read();
bool eulerianCycle();
void euler(int currentNode);
void write(bool status);

int main() {
	read();

	if(eulerianCycle()) {
		euler(1);
		write(true);
	}
	else
		write(false);

	return (0);
}

void read() {
	ifstream in("ciclueuler.in");
	int from,to;

	in >> nodes >> edges;

	for(int i=1;i<=edges;i++) {
		in >> from >> to;

		graph[from].push_back(to);
		graph[to].push_back(from);
	}

	in.close();
}

bool eulerianCycle() {
	for(int i=1;i<=nodes;i++)
		if(graph[i].size() % 2)
			return false;

	return true;
}

void euler(int currentNode) {
	list<int>::iterator firstIt,secondIt;
	int next;

	firstIt = graph[currentNode].begin();

	while(firstIt != graph[currentNode].end()) {
		next = *firstIt;
		secondIt = graph[next].begin();

		while(secondIt != graph[next].end()) {
			if(*secondIt == currentNode) {
				graph[next].erase(secondIt);
				break;
			}

			secondIt++;
		}

		graph[currentNode].pop_front();
		euler(next);
		firstIt = graph[currentNode].begin();
	}

	solution.push_back(currentNode);
}

void write(bool status) {
	ofstream out("ciclueuler.out");
	list<int>::iterator it=solution.begin();
	it++;

	if(status)
		for(;it!=solution.end();it++)
			out << *it << " ";
	else
		out << "-1\n";

	out.close();
}