#include<fstream>
#include<vector>
#include<stack>
#include<algorithm>
#include<queue>
using namespace std;

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


vector<int> v[100010];
int grad[100010];
int coada[100010],  nod, i, vizitat[100010], noduri, a, b, aux, n, m;
stack<int> st;

queue<int> q;

bool conex()
{
	q.push(1);
	vizitat[1] = 1;
	noduri = 1;
	while (!q.empty())
	{
		aux = q.front();
		q.pop();
		for (unsigned i = 0; i < v[aux].size(); ++i)
		{
			if (vizitat[v[aux][i]] == 0)
			{
				vizitat[v[aux][i]] = 1;
				q.push(v[aux][i]);
				noduri++;
			}
		}
	}
	if (noduri == n)
		return true;
	return false;
}

bool gradpar()
{
	for (int i = 1; i <= n; ++i)
		if (grad[i] % 2 != 0)
			return false;
	return true;
}
void cautaciclu()
{
	st.push(1);
	while (!st.empty())
	{
		int aux = st.top();
		if (v[aux].size())
		{
			int nod = v[aux].back(); v[aux].pop_back();
			st.push(nod);
			v[nod].erase(find(v[nod].begin(), v[nod].end(), aux));
		}
		else
		{
			st.pop();
			if (!st.empty())
				fout << aux << " ";
		}
	}

}
int main()
{
	int a, b;
	fin >> n >> m;
	for (int i = 1; i <= m; ++i)
	{
		fin >> a >> b;
		grad[a]++; grad[b]++;
		v[a].push_back(b); v[b].push_back(a);
	}
	if (conex() && gradpar())
	{
		cautaciclu();
	}
	else
		fout << "-1";
		//cout << "Nu exista ciclu!\n";
//	system("pause");


	return 0;
}