#include <bits/stdc++.h>
#define pb push_back
using namespace std;

ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");
const int VMAX=100009,EMAX=500009;
int v,e,i,x,y,from[EMAX],to[EMAX],sol[EMAX],nod,muchie,used[EMAX],k;
vector < int > g[VMAX];
stack < int > sk;
int main()
{
    fin >> v >> e;
    for(i = 1; i <= e; i++)
    {
        fin >> x >> y;
        g[x].pb(i);
        g[y].pb(i);
        from[i] = x;
        to[i] = y;
    }
    for(i = 1; i <= v ; i++)
        if(g[i].size() & 1)
        {
            fout << -1;
            return 0;
        }
    sk.push(1);
    while(!sk.empty())
    {
        nod=sk.top();
        if(!g[nod].empty())
        {
            int muchie = g[nod].back();
            g[nod].pop_back();
            if(!used[muchie])
            {
                used[muchie] = 1;
                if(from[muchie]==nod)
                    sk.push(to[muchie]);
                else
                    sk.push(from[muchie]);
            }
        }
        else
        {
            sol[++k]=nod;
            sk.pop();
        }
    }
    for(i = 1; i <  k; i++)
    fout << sol[i] << " ";
}