#include <fstream>
#include <vector>
#include <cstring>
using namespace std;

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

int n, m, grad[100001];
vector<int> adj[100001];
bool b[100001];

int dfs_cnt(int nod)
{
    int cnt = 1;

    b[nod] = 1;

    for (int i = 0; i < adj[nod].size(); i++)
    {
        int next = adj[nod][i];
        if (!b[next] && next)
            cnt += dfs_cnt(next);
    }
    return cnt;
}

int euler(int nod)
{
    while (adj[nod].size())
    {
        fout << nod << ' ';
        if (adj[nod].size() == 1)
        {
            int next = adj[nod][0], poz;
            for (int j = 0; j < adj[next].size(); j++)
                if (adj[next][j] == nod)
                {
                    poz = j;
                    break;
                }
            adj[nod].erase(adj[nod].begin());
            if (nod != next)
                adj[next].erase(adj[next].begin() + poz);
            nod = next;
            continue;
        }
        for (int i = 0; i < adj[nod].size(); i++)
        {
            int next = adj[nod][i];

            if (next)
            {
                for (int j = 1; j <= n; j++)
                    b[j] = 0;
                int cnt = dfs_cnt(next), poz;
                for (int j = 0; j < adj[next].size(); j++)
                    if (adj[next][j] == nod)
                    {
                        poz = j;
                        break;
                    }

                adj[nod][i] = 0;
                adj[next][poz] = 0;

                for (int j = 1; j <= n; j++)
                    b[j] = 0;
                if (dfs_cnt(next) != cnt)
                {
                    adj[nod][i] = next;
                    adj[next][poz] = nod;
                }
                else
                {
                    adj[nod].erase(adj[nod].begin() + i);
                    if (next != nod)
                        adj[next].erase(adj[next].begin() + poz);
                    i--;
                    nod = next;
                    break;
                }
            }
        }
    }
}


int main()
{
    int x, y, cnt_impar = 0, start = 1;

    fin >> n >> m;
    while (m--)
    {
        fin >> x >> y;
        adj[x].push_back(y);
        if (x != y)
            adj[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }

    for (int i = 1; i <= n; i++)
    {
        if (grad[i] % 2 == 1)
        {
            if (cnt_impar < 2)
            {
                cnt_impar++;
                start = i;
            }
            else
            {
                start = 0;
            }
        }
    }

    if (start == 0)
        fout << -1;
    else
        euler(start);
    return 0;
}