#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

struct muchie{
    int x, y;
};

const int nmax = 100001, mmax=5e5 + 1;
vector<int> G[nmax];
muchie edges[mmax];
vector<int> rez;
bool deleted[mmax];

int getNextNode(int node)
{
    while(!G[node].empty() && deleted[G[node].back()])
        G[node].pop_back();
    if(G[node].empty())
        return 0;
    int edgeId = G[node].back();
    deleted[edgeId] = 1;
    return edges[edgeId].x + edges[edgeId].y - node;
}

void euler(int nod)
{
    while(int vecin = getNextNode(nod))
    {
        euler(vecin);
    }
    rez.push_back(nod);
}

int main()
{
    int n, m;
    fin >> n >> m;
    for(int i=1; i<=m; i++)
    {
        int x, y;
        fin >> x >> y;
        edges[i]={x, y};
        G[x].push_back(i);
        G[y].push_back(i);
    }
    bool is_euler = 1;
    for(int i=1; i<=n; i++)
        is_euler = is_euler && (G[i].size()%2 == 0);
    if(!is_euler)
    {
        fout << -1;
        return 0;
    }
    euler(1);
    for(vector<int>::iterator it=rez.begin(); it<rez.end()-1; it++)
        fout << *it << ' ';
    return 0;
}