#include <fstream>
#include <bitset>
#include <vector>

#define Nmax 100009
#define Mmax 500009
using namespace std;

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

int N,M,x,y;
vector<int> G[Nmax], Cycle;
pair<int,int> E[Mmax];
bitset<Mmax> viz;

int IsEulerian()
{
     for(int i = 1; i <= N; ++i)
          if(G[i].size() & 1) return 0;
     return 1;
}

void DFS(int x)
{
	for(auto y : G[x])
		if (!viz[y])
		{
			viz[y] = 1;
			DFS(E[y].first + E[y].second - x);
		}
    Cycle.push_back(x);
}

int main()
{
	f >> N >> M;
	for(int i = 1; i <= M; ++i)
	{
        f >> x >> y;
        G[x].push_back(i) , G[y].push_back(i);      // G[x] retine muchiile in care apare x
        E[i] = {x, y};                              // E[i] retine muchia i a grafului ca pair<x, y>
	}

    if(IsEulerian())
    {
        DFS(1);
        for(size_t i = 0; i < Cycle.size() - 1; ++i)
            g << Cycle[i] << ' ';
        g << '\n';
     }
     else g << -1 << '\n';

     f.close();
     g.close();
     return 0;
}