#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#define NMAX 100005

using namespace std;

vector<pair<int,int>> g[NMAX];
vector<int> cycle;
vector<bool> used;

void dfs(int u) {
	for (auto v : g[u]) 
		if (!used[v.second]) {
			used[v.second] = true;
			dfs(v.first);
		}
	cycle.push_back(u);

}

int main()
{
	ifstream fin("ciclueuler.in");
	ofstream fout("ciclueuler.out");

	int n, m;

	fin >> n >> m;

	for (int i = 0;i < m;++i) {
		int x, y;
		fin >> x >> y;
		used.push_back(false);
		g[x].push_back({ y,i });
		g[y].push_back({ x,i });
	}

	dfs(1);
	if (cycle.size() - 1 < m)
		fout << "-1";
	else
		for (auto u : cycle)
			fout << u << ' ';

	return 0;
}