#include <fstream>
#include <algorithm>
#include <stack>
#include <vector>
class InParser
{
#pragma warning(disable:4996)
private:
	FILE* fin;
	char* buff;
	int sp;
	char read()
	{
		++sp;
		if (sp == 4096)
		{
			sp = 0;
			fread(buff, 1, 4096, fin);
		}
		return buff[sp];
	}
public:
	InParser(const char* nume)
	{
		sp = 4095;
		buff = new char[4096];
		fin = fopen(nume, "r");
	}
	InParser& operator >> (int& n)
	{
		int sgn = 1;
		char c;
		while (!isdigit(c = read()) && c != '-');
		if (c == '-')
		{
			n = 0;
			sgn = -1;
		}
		else
			n = c - '0';
		while (isdigit(c = read()))
			n = n * 10 + c - '0';
		n *= sgn;
		return *this;
	}
};

InParser fin("ciclueuler.in");
std::ofstream fout("ciclueuler.out");

const int NMAX = 1e5 + 2;

std::vector <int> g[NMAX];

void euler()
{
	std::stack <int> st;
	st.push(1);
	std::vector <int> cycle;
	while (!st.empty())
	{
		int node = st.top();
		if (!g[node].empty())
		{
			int new_node = g[node].back();
			g[node].pop_back();
			g[new_node].erase(std::find(g[new_node].begin(), g[new_node].end(), node));
			st.push(new_node);
		}
		else
		{
			st.pop();
			if (!st.empty())
				cycle.push_back(st.top());
		}
	}
	for (auto i : cycle)
		fout << i << " ";
	fout << "\n";
}

int n, x, y, m;

int main()
{
	fin >> n >> m;
	for (int i = 1; i <= m; ++i)
	{
		fin >> x >> y;
		g[x].push_back(y);
		g[y].push_back(x);
	}

	for (int i = 1; i <= n; ++i)
		if (!g[i].size() || g[i].size() & 1)
		{
			fout << "-1\n";
			return 0;
		}

	euler();

	fout.close();
	return 0;
}