#include <bits/stdc++.h>
#define N 100004
#define M 500100
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int A[M] , B[M] , E[N] , n , m , k , d[N];
int viz[M];
unsigned ind[M];
vector <int> L[M];///aici retin indicele muchiei(prin noduri pot trece de > 1 ori)
void Citire()
{
    int i;
    fin >> n >> m;
    for(i = 1; i <= m; i++)
    {
        fin >> A[i] >> B[i];
        L[A[i]].push_back(i);
        L[B[i]].push_back(i);
        d[A[i]]++;
        d[B[i]]++;
    }
    fin.close();
}
inline int EsteEuler()
{
    int i;
    for(i = 1; i <= n; i++)
        if(d[i] % 2 != 0)return 0;
    return 1;
}
void Constr(int nod)
{
    while(ind[nod] < L[nod].size())
    {
        int i = L[nod][ind[nod]++];
        if(viz[i] == 0)
        {
            viz[i] = 1;
            Constr(A[i] + B[i] - nod);
        }
    }
    E[++k] = nod;
}
int main()
{
    Citire();
    if(!EsteEuler())
    {
        fout << "-1";
        fout.close();
        return 0;
    }
    Constr(A[1]);
    for(int i = 1; i < k; i++)
        fout << E[i] << " ";
    fout.close();

    return 0;
}