#include <bits/stdc++.h>

using namespace std;

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

const int Nmax=5e5+2;
int n,m,lg;
int st[Nmax],dr[Nmax],sol[Nmax];
vector<int>L[Nmax];
bitset<Nmax>viz;

void Citire()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>st[i]>>dr[i];
        L[st[i]].push_back(i);
        L[dr[i]].push_back(i);
    }
}

bool Check()
{
    for(int i=1;i<=n;i++)
        if(L[i].size()%2)return 0;
    return 1;
}

void Dfs(int nod)
{
    for(auto i:L[nod])
        if(!viz[i])
        {
            viz[i]=1;
            Dfs(st[i]+dr[i]-nod);
        }

    sol[++lg]=nod;
}

int main()
{
    Citire();

    if(Check()==1)
    {
        Dfs(1);

        for(int i=lg;i>1;i--)
            fout<<sol[i]<<" ";
        fout<<"\n";
    }
    else fout<<"-1\n";

    fin.close();
    fout.close();
    return 0;
}