#include <fstream>
#include <stack>
#include <queue>
#include <list>
using namespace std;

#define NMAX 100000

int N;
list<int> adjList[NMAX+1];
int degree[NMAX+1];
bool visited[NMAX+1];
queue<int> bfs_queue;
stack<int> euler_stack;
list<int> cycle;

void readInput()
{
	int M, to, from;
	ifstream f("ciclueuler.in");
	f >> N >> M;
	for (int i=0;i<M;i++)
	{
		f >> from >> to;
		adjList[from].push_back(to);
		adjList[to].push_back(from);
		degree[from]++;
		degree[to]++;		
	}
	f.close();
}

void bfs(int s)
{
	visited[s] = true;
	bfs_queue.push(s);
	while (!bfs_queue.empty())
	{
		int x = bfs_queue.front();
		bfs_queue.pop();
		for (list<int>::iterator it = adjList[x].begin(); it != adjList[x].end(); it++)
		{
			if (!visited[*it])
			{
				bfs_queue.push(*it);
				visited[*it] = true;
			}
		}
	}
}

bool eulerian_test()
{
	bfs(1);
	for (int i=1;i<=N;i++)
	{
		if (!visited[i] || degree[i] &1)
		{
			return false;
		}
	}
	return true;
}

void euler(int s)
{
	while (!adjList[s].empty())
	{
		int x = adjList[s].front();
		euler_stack.push(s);
		degree[s]--;
		degree[x]--;
		adjList[s].pop_front();
		for (list<int>::iterator it = adjList[x].begin(); it != adjList[x].end(); it++)
		{
			if (*it == s)
			{
				adjList[x].erase(it);
				break;
			}
		}
		s = x;
	}
	cycle.push_back(s);
}

int main(void)
{
	ofstream g("ciclueuler.out");

	readInput();
	if (eulerian_test)
	{
		int s = 1;
		do 
		{
			euler(s);
			s = euler_stack.top();
			euler_stack.pop();
		} while (!euler_stack.empty());

		for (list<int>::iterator it = cycle.begin(); it != cycle.end(); it++)
		{
			g << *it << " ";
		}
		g<<"\n";
	}
	else 
	{
		g << "-1\n";
	}

	g.close();
	return 0;
}