#include <bits/stdc++.h>
using namespace std;

vector <pair <int, int>> graph[100005];
int grade[100005], vizitat[500005], visitedEdges[500005], currentEdge[100005];
vector <int> cycle;

void buildCycle(int node)
{
    while(currentEdge[node] < graph[node].size())
    {
        pair <int, int> edge=graph[node][currentEdge[node]];
        currentEdge[node]++;
        if(visitedEdges[edge.second]) continue;
        visitedEdges[edge.second]=1;
        buildCycle(edge.first);
    }
    cycle.push_back(node);
}

void dfs(int node)
{
    vizitat[node]=1;
    for(auto x: graph[node])
    {
        if(!vizitat[x.first])
        {
            dfs(x.first);
        }
    }
}

int main()
{
    ifstream fin("ciclueuler.in");
    ofstream fout("ciclueuler.out");
    int n, m;
    fin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int x, y;
        fin>>x>>y;
        graph[x].push_back({y, i});
        graph[y].push_back({x, i});
        grade[x]++;
        grade[y]++;
    }
    dfs(1);
    for(int i=1; i<=n; i++)
    {
        if(!vizitat[i] || grade[i]%2)
        {
            fout<<-1;
            return 0;
        }
    }
    buildCycle(1);
    cycle.pop_back();
    for(auto x: cycle)
    {
        fout<<x<< " ";
    }
    return 0;
}