#include <iostream>
#include <fstream>
#include <vector>
#define pb push_back
using namespace std;

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

int n,aux;
vector < vector < int > > v;
vector < int > grad;
vector < int >::iterator it;

void citire()
{
    int m,x,y;
    in>>n>>m;
    v.resize(n+1);
    grad.resize(n+1);
    for(int i=1;i<=m;i++)
    {
        in>>x>>y;
        v[x].pb(y);
        v[y].pb(x);
        grad[x]++;
        grad[y]++;
    }
}

bool eGrafEulerian()
{
    for(int i=1;i<=n;i++)
        if(grad[i]%2)
            return false;
    return true;
}

void cicluEulerian(int x)
{
    while(v[x].size())
    {
        aux=v[x].back();
        v[x].pop_back();
        for(it=v[aux].begin();it!=v[aux].end();it++)
            if(*it==x)
            {
                *it=v[aux].back();
                v[aux].pop_back();
                break;
            }
        cicluEulerian(aux);
    }
    out<<x<<' ';
}

int main()
{
    citire();
    if(eGrafEulerian())
        cicluEulerian(1);
    else
        out<<"-1";
    return 0;
}