#include <fstream>
#include <vector>
#define MX 100001
using namespace std;

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

struct muc
{
    int a,b;
};

int n,m;
vector<muc*> v[MX];
vector<int> sol;

void citire()
{
    int i,x,y;
    muc* mm;
    fin>>n>>m;
    for(i=1; i<=m; i++)
    {
        fin>>x>>y;
        mm = new muc;
        mm->a = x;
        mm->b = y;
        v[x].push_back(mm);
        v[y].push_back(mm);
    }
}

inline void DFS(int i)
{
    muc* u;
    int j;
    while(!v[i].empty())
    {
        u = v[i].back();
        v[i].pop_back();

        if(!u->a) delete u;
        else
        {
            if(u->a != i) j = u->a;
            else j = u->b;

            u->a = u->b = 0;
            DFS(j);
        }
    }

    if(v[i].empty())
    {
        sol.push_back(i);
    }
}

int main()
{
    bool ok;
    citire();
    DFS(1);

    if(sol.front() == sol.back()) ok = 1;
    else ok = 0;

    sol.pop_back();

    if(!ok) fout<<-1;
    else
    {
        vector<int>::iterator it;
        for(it=sol.begin(); it!=sol.end(); it++)
        {
            fout<<*it<<' ';
        }
    }

    fin.close(); fout.close();
    return 0;
}