#include <fstream>
//#include <iostream>
//#include<stdio.h>
#include <stack>
#include <vector>
#include <algorithm>

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector<int>G[100005];
vector<int>::iterator it;
stack<int>st;
int n,m,i,j,k,l,r,x,y,s,smax,viz[100005];
bool ok;
void dfs(int x)
{
    int q;
    viz[x]=1;
    for(int v=0;v<G[x].size();v++)
    {
        q=G[x][v];
        if(!viz[q])
        {
            dfs(q);
        }
    }
}
void euler(int node)
{


    while(!G[node].empty())
    {
        st.push(node);
       int other=G[node].back();
       // it=find(G[other].begin(),G[other].end(),node);
        G[other].erase(find(G[other].begin(),G[other].end(),node));
        G[node].pop_back();
        node=other;
    }



}
int main()
{
    fin>>n>>m;

    for(i=1;i<=m;i++)
    {
        fin>>x>>y;

        G[x].push_back(y);
        G[y].push_back(x);

    }

    for(i=1;i<=n;i++)
        if(int((G[i].size())&1))
        ok=1;

    if(!ok)
    {

       l=1;
       fout<<1<<" ";

       do
        {
            euler(l);
            l=st.top();
            fout<<l<<" ";

            st.pop();

        }while(st.size()>1);

    }
    else
        fout<<-1<<"\n";


    return 0;
}