#include <fstream>
#include <vector>

using namespace std;

const int M = 500001;
const int N = 100001;

struct muchie
{
    int x, y;
    bool folosit;
};

muchie e[M];
vector <int> a[N];
int c[M+1], ne, ind[2*M], urm[2*M], lst[N], nr;

void euler(int x)
{
    //for (auto i: a[x])
    for (int p = lst[x]; p != 0; p = urm[p])
    {
        int i = ind[p];
        if (e[i].folosit)
        {
            continue;
        }
        e[i].folosit = true;
        int y = e[i].x + e[i].y - x;
        euler(y);
    }
    //c.push_back(x);
    c[ne++] = x;
}

void adauga(int x, int i)
{
    ind[++nr] = i;
    urm[nr] = lst[x];
    lst[x] = nr;
}

int main()
{
    ifstream in("ciclueuler.in");
    ofstream out("ciclueuler.out");
    int n, m;
    in >> n >> m;
    for (int i = 0; i < m; i++)
    {
        in >> e[i].x >> e[i].y;
        //a[e[i].x].push_back(i);
        adauga(e[i].x, i);
        //a[e[i].y].push_back(i);
        adauga(e[i].y, i);
    }
    in.close();
    euler(1);
    //if (c.size() == m + 1)
    if (ne == m + 1 && c[0] == c[ne-1])
    {
        //c.erase(c.begin() + m);
        ne--;
        //for (auto x: c)
        for (int i = 0; i < ne; i++)
        {
            int x = c[i];
            out << x << " ";
        }
    }
    else
    {
        out << -1;
    }
    out.close();
    return 0;
}