#include <vector>
#include <fstream>
#include <set>
#include <queue>
using namespace std;

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

vector <bool> viz;
vector <multiset <int> > g;
vector <int> st;
queue <int> Q;
int n, m;

void bfs(int x) {
	viz[x] = 1;
	Q.push(x);
	while (Q.size()) {
		x = Q.front();
		Q.pop();
		for (multiset <int> :: iterator it = g[x].begin(); it != g[x].end(); ++it)
			if (!viz[*it]) {
				Q.push(*it);
				viz[*it] = 1;
			}
	}
}

bool verif() {
	for (int i = 1; i <= n; ++i)
		if (g[i].size() & 1 || (!viz[i] && g[i].size()))
			return 0;
	return 1;
}

int main() {
	fin >> n >> m;
	viz.resize(n+1);
	g.resize(n+1);
	while (m--) {
		int x, y;
		fin >> x >> y;
		g[x].insert(y);
		g[y].insert(x);
	}
	int x = 0;
	for (int i = 1; i <= n && !x; ++i)
		x = (g[i].size()) ? i : 0;
	bfs(x);
	if (!verif()) {
		fout << -1;
		return 0;
	}
	st.push_back(*g[x].begin());
	int y = st.back();
	g[x].erase(g[x].begin());
	g[y].erase(x);
	while (st.size()) {
		int now = st.back();
		if (!g[now].size()) {
			fout << now << " ";
			st.pop_back();
			continue;
		}
		int y = *g[now].begin();
		g[now].erase(g[now].begin());
		g[y].erase(g[y].find(now));
		st.push_back(y);
	}
	fout.close();
}