#include<iostream>
#include<fstream>
#include<list>
#include<vector>
#include<stack>
#include<algorithm>

using namespace std;

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

int N,M;
bool Use[100005],OK;

list <int> G[100005];
vector <int> Sol;
stack <int> S;

void Read()
{
    fin>>N>>M;

    for(int i=1;i<=M;i++)
    {
        int x,y;
        fin>>x>>y;

        G[x].push_back(y);
        G[y].push_back(x);
    }
}

void Solve()
{
    for(int i=1;i<=N;i++)
        if(G[i].size()%2 || G[i].size()==0)
        {
            fout<<"-1\n";
            return;
        }

    OK = 1;

    S.push(1);

    while(!S.empty())
    {
        int Nod = S.top();

        while(G[Nod].size())
        {
            int Vecin=G[Nod].front();

            G[Nod].pop_front();
            G[Vecin].erase(find(G[Vecin].begin(),G[Vecin].end(),Nod));

            S.push(Vecin);

            Nod=Vecin;
        }

        Sol.push_back(S.top());
        S.pop();
    }

}

void Print()
{
    Sol.pop_back();

    for(int i=0;i<(int)Sol.size();i++)
        fout<<Sol[i]<<" ";
    fout<<"\n";
}

int main()
{
    Read();
    Solve();

    if(OK)
    Print();

    return 0;
}