#include<iostream>
#include<fstream>
#include<list>
#include<vector>
#include<stack>
#include<algorithm>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int NMax=100005;
int N,M,k;
bool OK;
list <int> G[NMax];
stack <int> S;
vector <int> Sol;

 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;
}