#include <bits/stdc++.h>

using namespace std;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int N=100010;


vector<pair<int,int>> adj[N];
int n,m,st,dr;
int f[N],v[N];

int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        adj[x].push_back(make_pair(y,i));
        adj[y].push_back(make_pair(x,i));
    }

    for(int i=1;i<=n;i++)
    {
        if(adj[i].size() % 2 == 1)
        {
            fout<<-1;
            return 0;
        }
    }

    deque <int> d = {};

    d.push_front(1);

    while(!d.empty())
    {
        int nod = d.front();

        if(adj[nod].size()!=0)
        {
            int x = adj[nod][adj[nod].size()-1].second;
            if(f[x] == 0)
            {
                f[x] = 1;
                d.push_front(adj[nod][adj[nod].size() -1].first);
            }
            adj[nod].pop_back();
        }
        else
        {
            v[++st] = nod;
            d.pop_front();
        }
    }
    for(int i=1;i<=st;i++)
        fout<<v[i]<<" ";
}