#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <queue>

using namespace std;

vector<vector<long long> > graf;
vector<long long> ciclu;
vector<long long>::iterator it;
queue<long long>q;
long long n,m;

void euler (long long v)
{
    q.push(v);

    while(!q.empty())
    {
        long long w;
        v = q.front(); q.pop();
        while(graf[v].size())
        {
            w = *graf[v].begin();
            graf[v].erase(graf[v].begin());

            it=find(graf[w].begin(), graf[w].end(), v);
            graf[w].erase(it);
            q.push(w);
        }
        ciclu.push_back(v);
    }

}
int main()
{
    ifstream f("ciclueuler.in");
    ofstream g("ciclueuler.out");
    long long i,u,v;
    unsigned isEuler=1;
    f>>n>>m;
    graf.resize(n+1);
    for(i=1;i<=m;i++)
    {
        f>>u>>v;
        graf[u].push_back(v);
        graf[v].push_back(u);
    }
    for(i=1;i<=n;i++)
    {
        cout<<graf[i].size()<<' ';
        if(graf[i].size()%2==1){
            isEuler=0;break;
        }
    }
    if(isEuler)euler(1);
    else g<<-1;
    for(i=0;i<ciclu.size()-1;i++)
        g<<ciclu[i]<<' ';
    return 0;
}