#include <fstream>
#include <vector>
#include <stack>
#define NMax 100005
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

int N,M;
vector <int> G[NMax],Sol;
stack <int> S;
int Grad[NMax],Ok=1,Use[NMax];

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++)
    {
        int Vecin = G[Nod][i];
        if(!Use[Vecin])
            DFS(Vecin);
    }
}

void Erase(int Nod1, int Nod2)
{
    G[Nod1].erase(G[Nod1].begin());

    for(unsigned int i = 0; i<G[Nod2].size(); i++)
        if(G[Nod2][i]==Nod1)
        {
            G[Nod2].erase(G[Nod2].begin()+i);
            break;
        }
}

void Cycle(int Nod)
{
    while(G[Nod].size())
    {
        S.push(Nod);
        int Vecin = G[Nod][0];
        Erase(Nod,Vecin);
        Nod = Vecin;
    }
}

void Solve()
{
    DFS(1);

    for(int i = 1; i<=N; i++)
        if(Grad[i]%2==1)
            Ok=0;
    for(int i = 1; i<=N; i++)
        if(!Use[i])
            Ok=0;
    if(!Ok) 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(unsigned int i = 0 ; i<Sol.size(); i++)
        fout<<Sol[i]<<" ";
    fout<<"\n";
}

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