#include <fstream>
#include <vector>

using namespace std;

bool even ();
void DFS (unsigned int node);

unsigned int N, M;
unsigned int u[500001], v[500001];

vector <unsigned int> L[500001];
bool seen[500001];
unsigned int pos[500001], q[500001];
unsigned int k, K;
unsigned int i;

int main ()
{
    ifstream fin ("ciclueuler.in");
    fin >> N >> M;
    for (i=1; i<=M; i++)
    {
        fin >> u[i] >> v[i];
        L[u[i]].push_back(i);
        L[v[i]].push_back(i);
    }
    fin.close();
    ofstream fout ("ciclueuler.out");
    if (!even())
        fout << -1;
    else
    {
        DFS(1);
        for (i=1; i<k; i++)
            fout << q[i] << ' ';
        fout << '\n';
    }
    fout.close();
    return 0;
}

bool even ()
{
    for (i=1; i<=N; i++)
        if (L[i].size()%2 != 0)
            return 0;
    return 1;
}

void DFS (unsigned int node)
{
    while (pos[node] < L[node].size())
    {
        K = L[node][pos[node]];
        pos[node]++;
        if (!seen[K])
        {
            seen[K] = 1;
            DFS(u[K]+v[K]-node);
        }
    }
    q[++k] = node;
}