#include<bits/stdc++.h>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector<pair<pair<int,int>,int>>v[100001];
vector<int>rez;
int viz[100001],m;
void dfs(int x)
{
    viz[x]=true;
    for(auto q:v[x])
    {
        if(!viz[q.first.first])
        {
            dfs(q.first.first);
        }
    }
}
void dfs2(int x)
{
    for(auto &q:v[x])
        if(q.first.second!=1)
        {
            q.first.second=1;
            v[q.first.first][q.second].first.second=1;
            dfs2(q.first.first);
        }
    rez.push_back(x);
}
int main()
{
    int n;
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int a,b;
        fin>>a>>b;
        if(a!=b)
        {
            v[a].push_back({{b,0},v[b].size()});
            v[b].push_back({{a,0},v[a].size()-1});
        }
        else
        {
            v[a].push_back({{b,0},v[b].size()+1});
            v[b].push_back({{a,0},v[a].size()-1});
        }
    }
    for(int i=1;i<=n;i++)
    {
        if(v[i].size()%2==1)
        {
            fout<<-1;
            return 0;
        }
    }
    dfs(1);
    if(*min_element(viz+1,viz+n+1)==false)
    {
        fout<<-1;
        return 0;
    }
    dfs2(1);
    rez.pop_back();
    for(auto q:rez)
        fout<<q<<" ";
}