#include <fstream>
#include <vector>
#include <stack>
#define NMAX 100003
using namespace std;

int n, m;
int x, y;
int grad[NMAX];
int start[NMAX];
bool viz[500003];


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

struct val {
    int vecin, indMuchie;
};

vector<val>graf[NMAX];

int main()
{
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        fin >> x >> y;
        //pun muchiile in lista
        grad[x]++;
        grad[y]++;
        graf[x].push_back({ y,i });
        graf[y].push_back({ x,i });

    }

    for (int i = 1; i <= n; i++)
    {
        if (grad[i] % 2 == 1)
        {
            fout << "-1";
            return 0;
        }

    }


    stack<int>stiva;
    stiva.push(1);
    vector<int>sol;
    while (!stiva.empty())
    {
        int nod = stiva.top();
        if (grad[nod] == 0)
        {
            //fout<<nod;
            sol.push_back(nod);
            stiva.pop();
            continue;
        }
        //parcurg muchiile sa verific daca mai pot lua o muchie
        for (int i = start[nod]; i < graf[nod].size(); i++)
        {
            int cod = graf[nod][i].indMuchie;
            int nd = graf[nod][i].vecin;
            start[nod]++;
            if (!viz[cod])
            {
                viz[cod] = true;
                
                stiva.push(nd);
                grad[nod]--;
                grad[nd]--;
                break;
            }

        }
    }
    if (sol.size() != m + 1)
    {
        fout << "-1";
        return 0;
    }
    for (int i = 0; i < sol.size() - 1; i++)
    {
        fout << sol[i] << " ";
    }
    return 0;
}