#include <bits/stdc++.h>
#define N 100005
#define M 500505

using namespace std;

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

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

void Read()
{
    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);
        h[A[i]].push_back(B[i]);
        h[B[i]].push_back(A[i]);
        d[A[i]]++;
        d[B[i]]++;
    }
}

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

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

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

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