#include <bits/stdc++.h>
#define N 100001
#define M 500501

using namespace std;

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

vector <int> L[N];
vector <int> h[N];
bitset <M> viz;
int n, m, d[N], E[M], A[M], B[M], ind[N], k;

void Citire()
{
    fin >> n >> m;
    for(int i = 1 ; i <= m ; i++)
    {
        fin >> A[i] >> B[i];
        L[A[i]].push_back(i);
        L[B[i]].push_back(i);
        h[A[i]].push_back(B[i]);
        h[B[i]].push_back(A[i]);
        d[A[i]]++;
        d[B[i]]++;
    }
    fin.close();
}

void DFS(int nod)
{
    viz[nod] = 1;
    for(auto i : h[nod])
        if(viz[i] == 0)
            DFS(i);
}

int EsteEulerian()
{
    DFS(A[1]);
    for(int i = 1 ; i <= n ; i++)
    {
        if(d[i]%2 == 1)
            return 0;
        if(d[i]>0 && viz[i] == 0)
            return 0;
    }
    return 1;
}

void Euler(int nod)
{
    while(ind[nod] < L[nod].size())
    {
        int i = L[nod][ind[nod]++];
        if(viz[i] == 0)
        {
            viz[i] = 1;
            Euler(A[i] + B[i] - nod);
        }
    }
    E[++k] = nod;
}

int main()
{
    Citire();
    if(!EsteEulerian())
    {
        fout << "-1\n";
        fout.close();
        return 0;
    }
    viz.reset();
    Euler(A[1]);
    for (int i = 1; i < k; i++)
        fout << E[i] << " ";
    fout << "\n";

    fout.close();
    return 0;
}