#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int NMax = 100000;
vector <int> G[NMax + 5];
int Use[NMax + 5]; int Grad[NMax + 5];
stack <int> S;
vector <int> Sol;
int N,M,Ok;
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(auto Vecin : G[Nod])
    {
        if(!Use[Vecin])
            DFS(Vecin);
    }
}
void Delete(int Nod1, int Nod2)
{
    G[Nod1].erase(G[Nod1].begin());
    for(int i = 0; i < (int)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())
    {
        int NewNod = G[Nod][0];
        Delete(Nod,NewNod);
        S.push(Nod);
        Nod = NewNod;
    }
}
void Solve()
{
    DFS(1);
    Ok = 1;
    for(int i = 1; i <= N; ++i)
        if(!Use[i])
            Ok = 0;
    for(int i = 1; i <= N; ++i)
        if(Grad[i]%2)
            Ok = 0;
    if(Ok)
    {
    int Nod = 1;
    do
    {
         Cycle(Nod);
         Nod = S.top();
         S.pop();
         Sol.push_back(Nod);

    }while(!S.empty());
    }
}

void Print()
{
    if(Ok == 0)
        {
             fout << "-1\n";
             return;
        }


    for(auto i : Sol)
        fout << i << " ";
    fout << "\n";
}
int main()
{
    Read();
    Solve();
    Print();
}