#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;
   /*
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d %d\n",&n,&m);*/
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        //scanf("%d %d\n",&x,&y);
        G[x].push_back(y);
        G[y].push_back(x);
 
    }
    
    for(i=1;i<=n;i++)
        if(G[i].size()%2==1)
        ok=1;
    /*if(!ok)
        {
            dfs(1);
            for(i=1;i<=n;i++)
            if(!viz[i])
                ok=1;
        }*/
    if(!ok)
    {
        //st.push(1);
 
       // fout<<1<<" " ;
       l=1;
       fout<<1<<" ";
       // printf("1 ");
       do
        {
            euler(l);
            l=st.top();
            fout<<l<<" ";
             //printf("%d ",l);
            st.pop();
 
        }while(st.size()>1);
 
    }
    else
       // printf("-1\n");
        fout<<-1<<"\n";
    // fout<<st.size();
 
    return 0;
}