#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], Sol;
stack <int> Stack;
int Use[NMax + 5],Grad[NMax + 5];
int N,M;
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);
    }
}

int Check()
{
    DFS(1);
    for(int i = 1; i <= N; ++i)
        if(Use[i] == 0 or Grad[i] % 2)
            return 0;
    return 1;
}

void Delete(int Nod, int Vecin)
{
    G[Nod].erase(G[Nod].begin());
    for(int i = 0; i < (int)G[Vecin].size(); ++i)
    {
        if(G[Vecin][i] == Nod)
        {
            G[Vecin].erase(G[Vecin].begin() + i);
            return;
        }
    }
}
void Cycle(int Nod)
{
    while(G[Nod].size())
    {
        int Vecin = G[Nod][0];
        Stack.push(Nod);
        Delete(Nod,Vecin);
        Nod = Vecin;
    }
}
void Solve()
{
    int Nod =1;
    do
    {
        Cycle(Nod);
        Nod = Stack.top();Stack.pop();
        Sol.push_back(Nod);
    }
    while (!Stack.empty());
}
void Print()
{
    for(auto i : Sol)
        fout << i << " ";
    fout <<"\n";
}
int main()
{
    Read();
    if(!Check())
    {
        fout << -1 << "\n";
        return 0;
    }
    Solve();
    Print();
    return 0;
}