//Code by Patcas Csaba
//Time complexity:
//Space complexity:
//Method:
//Implementation time: 

#include <vector>
#include <string> 
#include <set> 
#include <map> 
#include <queue> 
#include <bitset> 
#include <stack>
#include <list>

#include <numeric> 
#include <algorithm> 

#include <cstdio>
#include <fstream>
#include <iostream> 
#include <sstream> 
#include <iomanip>

#include <cctype>
#include <cmath> 
#include <ctime>
#include <cassert>

using namespace std;

#define LL long long
#define PII pair <int, int>
#define VB vector <bool>
#define VI vector <int>
#define VD vector <double>
#define VS vector <string>
#define VPII vector <pair <int, int> >
#define VVI vector < VI >
#define VVB vector < VB >

#define FORN(i, n) for(int i = 0; i < (n); ++i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORI(it, X) for(__typeof((X).begin()) it = (X).begin(); it !=(X).end(); ++it) 
#define REPEAT do{ 
#define UNTIL(x) }while(!(x)); 

#define SZ size()
#define BG begin() 
#define EN end() 
#define CL clear()
#define X first
#define Y second
#define RS resize
#define PB push_back
#define MP make_pair
#define ALL(x) x.begin(), x.end()

#define in_file "ciclueuler.in"
#define out_file "ciclueuler.out"
ifstream fin(in_file);
ofstream fout(out_file);

int n, m;
vector < list <int> > g;
VI gr, sol;
VB was;

inline void AddEdge(int x, int y)
{
	g[x].PB(y);
	g[y].PB(x);
	++gr[x];
	++gr[y];
}

inline void RemoveEdge(int x, int y)
{
	list<int> :: iterator i = g[x].BG;
	while (*i != y) ++i;
	g[x].erase(i);
	i = g[y].BG;
	while (*i != x) ++i;
	g[y].erase(i);
	--gr[x];
	--gr[y];
}

inline bool Euler()
{
	FOR(i, 1, n)
		if (gr[i] & 1) return false;
	return true;
}

void Bf()
{
	queue <int> fifo;
	fifo.push(1);
	was[1] = true;
	while (!fifo.empty())
	{
		int head = fifo.front();
		for(list<int> :: iterator i = g[head].BG; i != g[head].EN; ++i)
		{
			int aux = *i; 
			if (!was[aux])
			{
				was[aux] = true;
				fifo.push(aux);
			}
		}
		fifo.pop();
	}
}

bool Connected()
{
	fill(ALL(was), false);
	Bf();
	FOR(i, 1, n)
		if (gr[i] && !was[i]) return false;
	return true;
}

void Fleury()
{
	was.RS(n + 1);
	int node = 1;
	while (sol.SZ < m)
	{
		sol.PB(node);
		int found = -1;
		FORN(i, gr[node])
		{
			list<int> :: iterator it = g[node].BG;
			int aux = *it;
			RemoveEdge(node, aux);
			if (Connected())
			{
				found = aux;
				break;
			}
			AddEdge(node, aux);
		}
		if (found != -1) node = found;
		else 
		{
			found = *g[node].BG;
			RemoveEdge(node, found);
			node = found;
		}
	}
}

int main()
{
	//Read data
	fin >> n >> m;
	g.RS(n + 1);
	gr.RS(n + 1);
	FORN(i, m)
	{
		int x, y;
		fin >> x >> y;
		AddEdge(x, y);
	}
	fin.close();

	//Solve
	if (!Euler())
	{
		fout << -1;
		fout.close();
		return 0;
	}
	
	Fleury();

	//Write data
	FORN(i, sol.SZ) fout << sol[i] << " ";
	fout.close();

	return 0;
}