#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int NMax = 100000;
int N,M;
int Use[NMax + 5],Degree[NMax + 5];
vector <int> G[NMax+5],Sol;
stack <int> Stack;
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);
        Degree[x]++;
        Degree[y]++;
    }
}

void DFS(int Nod)
{
    Use[Nod] = 1;
    for(int i = 0; i < (int)G[Nod].size(); ++i)
    {
        int Vecin = G[Nod][i];
        if(!Use[Vecin])
            DFS(Vecin);
    }
}

void Delete(int X, int Y)
{
    G[X].erase(G[X].begin());
    for(int i = 0; i < (int)G[Y].size(); ++i)
        if(G[Y][i] == X)
        {
            G[Y].erase(G[Y].begin() + i);
            break;
        }
}
void FindCycle(int Nod)
{
    while(G[Nod].size())
    {
        int Vecin = G[Nod][0];
        Stack.push(Nod);
        Delete(Nod,Vecin);
        Nod = Vecin;
    }
}

void Euler()
{
    int Nod = 1;
    do
    {
        FindCycle(Nod);
        int NewNode=Stack.top();
        Stack.pop();
        Sol.push_back(NewNode);
        Nod = NewNode;
    }while(!Stack.empty());

}

void Print()
{
    for(int i = 0; i < (int)Sol.size(); ++i)
        fout << Sol[i] << " ";
    fout << "\n";
}

int main()
{
    Read();
    DFS(1);
    int Ok = 1;
    for(int i = 1; i <= N; ++i)
    {
        if (Use[i] == 0)
            Ok = 0;
        if(Degree[i]%2)
            Ok = 0;
    }
    if(Ok)
    {
        Euler();
        Print();
    }
    else
        fout << "-1\n";
    return 0;
}