#include <fstream>
#include <vector>
#include <stack>
#define NMax 100002
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector <int> G[NMax];
int N,M,Grad[NMax],Use[NMax],Ok=1;
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);
        Grad[x]++;Grad[y]++;
    }
}
void DFS(int Nod)
{
    Use[Nod]=1;
    for(unsigned int i=0;i<G[Nod].size();i++)
        {
            if(!Use[G[Nod][i]])
                DFS(G[Nod][i]);
        }
}
void Cycle(int Nod)
{
    while(G[Nod].size())
        {
            int Vecin=G[Nod][0];
            S.push(Vecin);
            G[Nod].erase(G[Nod].begin());
            for(vector <int> :: iterator it=G[Vecin].begin();it!=G[Vecin].end();it++)
                if(*it==Nod)
                    {
                        G[Vecin].erase(it);
                        break;
                    }
            Nod=Vecin;
        }
}
void Solve()
{
    DFS(1);
    for(int i=1;i<=N;i++)
        {
            if(Grad[i]%2 || !Use[i])
                {
                Ok=0;
                return;
                }
        }
    int Nod=1;
    do
    {
    Cycle(Nod);
    Nod=S.top();S.pop();
    Sol.push_back(Nod);
    }while(!S.empty());

}
void Print()
{
    if(!Ok)
    {
        fout<<"-1\n";
        return;
    }
    for(int i=0;i<Sol.size();i++)
        fout<<Sol[i]<<" ";
    fout<<"\n";

}
int main()
{
    Read();
    Solve();
    Print();
    return 0;
}