#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 N,M;
int Use[NMax + 5];
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);
    }
}

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(G[i].size() % 2)
            return 0;
    for(int i = 1; i <= N; ++i)
        if(!Use[i])
            return 0;
    return 1;
}

void Print()
{
    if(!Check())
    {
        fout << "-1\n";
        return;
    }
    for(auto i : Sol)
    {
        fout << i << " ";
    }
    fout << "\n";
}

void Delete(int A, int B)
{
    G[A].erase(G[A].begin());
    for(int i = 0; i < (int)G[B].size(); ++i)
        if(G[B][i] == A)
        {
            G[B].erase(G[B].begin() + i);
            break;
        }
}

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);
        int LastNod = Stack.top(); Stack.pop();
        Sol.push_back(LastNod);
        Nod = LastNod;
    }while(!Stack.empty());
}

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