#include <fstream>
#include <vector>
#define nmax 100005
#define mmax 500005
using namespace std;
ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");
vector <pair<int, int> > v[nmax];
int n, m, viz[mmax], nrl, l[mmax], gr[nmax];

void citire()
{
    int i, x, y;
    cin>>n>>m;
    for(i=1; i<=m; i++)
    {
        cin>>x>>y;
        v[x].push_back({y, i});
        v[y].push_back({x, i});
        gr[x]++; gr[y]++;
        //mu[i].x=x; mu[i].y=y;
    }
}
void euler(int nod)
{
    int vec, ind;
    while(v[nod].size()>0)
    {
        vec=v[nod].back().first; ind=v[nod].back().second;
        if(!viz[ind])
        {
            viz[ind]=1;
            v[nod].pop_back();
            euler(vec);
        }
        else v[nod].pop_back();
    }
    nrl++; l[nrl]=nod;
}
void afis()
{
    int i;
    for(i=1; i<nrl; i++)
        cout<<l[i]<<' ';
}
int ok()
{
    int i;
    for(i=1; i<=n; i++)
        if(gr[i]%2==1) return 0;
    return 1;
}
int main()
{
    citire();
    if(ok())
    {
    euler(1);
    afis();
    }
    else cout<<-1;
    return 0;
}