#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

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

const int dimN = 100001;
const int dimM = 500001;
int noduri, muchii;
stack<int>st;
bool sters[dimM];
int grade[dimN];
vector<int>ciclu;

struct muchie {
	int nod, nrMuchie;
};

vector<muchie>G[dimN];

void citire() {
	int c = 0;
	in >> noduri >> muchii;
	for (int i = 0; i < muchii; i++) {
		int x, y;
		in >> x >> y;
		grade[x]++;
		grade[y]++;
		c++;
		muchie m;
		m.nrMuchie = c;
		m.nod = y;
		G[x].push_back(m);
		m.nod = x;
		G[y].push_back(m);
	}
	return;
}

bool areEuler() {
	for (int i = 1; i <= noduri; i++) {
		if (grade[i] & 1) {
			return false;
		}
	}
	return true;
}

void cicluE(int nod) {
	st.push(nod);

	while (st.empty() == false) {
		int nod = st.top();
		if (G[nod].size()) {
			int vecin = G[nod].back().nod;
			int muchie = G[nod].back().nrMuchie;
			G[nod].pop_back();
			if (!sters[muchie]) {
				sters[muchie] = 1;
				st.push(vecin);
			}
		}
		else {
			ciclu.push_back(nod);
			st.pop();
		}
	}
	return;
}

int main() {

	citire();
	if (!areEuler()) {
		out << "-1\n";
		return 0;
	}

	cicluE(1);
	int k = ciclu.size();
	for (int i = 0; i < k - 1; i++) {
		out << ciclu[i] << " ";
	}

	return 0;
}