#include <fstream>
#include <vector>
#include <queue>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
//------------------------------------------
//Variabile globale
int n,m;
vector<vector<pair<int,int>>>v;
queue<int>sol;
//------------------------------------------
//Functii
void citire();
bool verificare(),verificare2();
void ciclu();
void afisare();
//------------------------------------------
int main()
{
	citire();
	if(!verificare() or !verificare2())
	{
		g << -1;
		return 0;
	}
	ciclu();
	afisare();
	return 0;
}
//------------------------------------------
void citire()
{
	f >> n >> m;
	v.resize(n + 1);
	for(int i = 1; i <= n; ++i)
		v[i].push_back({0,0});
	int x,y;
	for(int i = 1; i <= m; ++i)
	{
		f >> x >> y;
		v[x].push_back({y,i});
		v[y].push_back({x,i});
	}
}
//------------------------------------------
bool verificare()
{
	for(int i = 1; i <= n; ++i)
	{
		v[i][0].first = v[i].size() - 1;
		if(v[i].size() & 1 == 0 or v[i].size() == 1)
			return false;
	}
	return true;
}
//------------------------------------------
void ciclu()
{
	int st[500001],nr = 1;
	st[nr]=1;
	bool ap[500001];
	while(nr)
	{
		int i = v[st[nr]][0].first;
		while(i > 0 && ap[v[st[nr]][i].second])
			i--;
		v[st[nr]][0].first = i - 1;
		if(i > 0)
		{
			nr++;
			st[nr] = v[st[nr - 1]][i].first;
			ap[v[st[nr - 1]][i].second] = 1;
		}
		else
		{
			sol.push(st[nr]);
			nr--;
		}
	}
}
//------------------------------------------
void afisare()
{
	while(!sol.empty() && sol.size() != 1)
	{
		g << sol.front() << " ";
		sol.pop();
	}
}
//------------------------------------------
bool verificare2()
{
	queue<int>q;
	bool ap[100001];
	for(int i = 1;i <= n;++i)
        ap[i]=0;
	q.push(1);
	ap[1]=1;
	while(!q.empty())
	{
		int x = q.front();
		q.pop();
		for(int i = 1; i < v[x].size(); ++i)
			if(ap[v[x][i].first] == 0)
			{
				ap[v[x][i].first] = 1;
				q.push(v[x][i].first);
			}
	}
	for(int i = 1;i <= n;++i)
        if(ap[i]!=1)
            return false;
    return true;
}