#include <iostream>
#include <cstdio>
#include <vector>
#define N 100005

using namespace std;

int n, m, vecin;

vector <int> G[N];

int verificare()
{
    for(int i = 1 ; i <= n ; ++i)
    {
        if(G[i].size() % 2)
        {
            return 1;
        }
    }
    return 0;
}

vector <int>::iterator it;

void stergere(int k, int x)
{
    for(it = G[k].begin() ; it != G[k].end() ; ++it)
    {
        if(*it == x)
        {
            G[k].erase(it);
            break;
        }
    }
}

void euler(int k)
{
    while(!G[k].empty())
    {
        vecin = G[k].back();

        G[k].pop_back();

        stergere(vecin,k);

        euler(vecin);
    }

    printf("%d ",k);
}

void citire()
{
    scanf("%d %d\n",&n,&m);

    int a,b;

    for(int i = 1 ; i <= m ; ++i)
    {
        scanf("%d %d\n",&a,&b);

        G[a].push_back(b);
        G[b].push_back(a);
    }

    if(verificare())
    {
        printf("-1");
    }
    else
    {
        euler(1);
    }
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);

    citire();

    return 0;
}