#include<fstream>
#include<vector>
using namespace std;
#define maxn 100005
#define maxm 500005
int n,m,g[maxn],stiva[maxm],rez[maxm] , prim=1, ultim=1,k=1;
vector <int>v[maxn];
ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");

void read(){
    int x,y;
    for(int i=1; i<=m; i++){
        cin>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
        g[x]++; g[y]++;
    }
}

void euler(){
    while(prim>0){
        while(g[stiva[prim]]){
            stiva[++ultim]=v[stiva[prim]][g[stiva[prim]]-1];
            v[stiva[prim]].pop_back();
            g[stiva[prim]]--;
                for(int i=0; i<g[stiva[ultim]]; i++){
                if(v[stiva[ultim]][i]==stiva[prim]){
                    v[stiva[ultim]].erase (v[stiva[ultim]].begin()+i);
                    g[stiva[ultim]]--;
                    break;
                }
            }
            prim++;
        }
        rez[k++]=stiva[prim];
        if(k-2==m)
            return;
        prim--;
        ultim--;
    }
}


int main(){
    cin>>n>>m;
    read();
    for(int i=1; i<=n; i++)
        if(g[i]&1){
            cout<<-1<<'\n';
            return 0;
        }
    stiva[1]=1;
    euler();
    k-=2;
    for(int i=1; i<=k; i++)
        cout<<rez[i]<<' ';
    return 0;
}




/*
#include <iostream>
#include <cstring>
#include <vector>
//std::ifstream cin("ciclueuler.in");
//std::ofstream cout("ciclueuler.out");
using namespace std;
#define maxn 500505
vector<int> G[maxn];
bool used_edge[maxn];
int from[maxn],to[maxn], N,M;

void citire(){
    int x,y;
    cin>>N>>M;
    for(int i=1;i<=M;i++){
        cin>>x>>y;
        G[x].push_back(i);
        G[y].push_back(i);
        from[i]=x;
        to[i]=y;
    }
}


int main()
{
    int node;
    citire();
    for(int i=1;i<=N;i++)
        if(G[i].size()&1){
            cout<<"-1\n";
            return 0;
    }
    vector<int> ans,stk;
    stk.push_back(1);
    while(!stk.empty()){
        node=stk.back();
        if(!G[node].empty()){
            int e=G[node].back();
            G[node].pop_back();
            if(!used_edge[e]){// ::reprezinta in cazul de fata from si to , cele declarate global.
                used_edge[e]=true;//^operator pe biti xor, pe scurt stk.push_back(to[e]);
                int to=from[e] ^ ::to[e] ^ node;//pt ca node==from[e];
                stk.push_back(to);
            }
        }else{
            stk.pop_back();
            ans.push_back(node);
        }
    }
     for(vector<int>::iterator it=ans.begin();it!=ans.end()-1;it++)
        cout<<*it<<' ';

    return 0;
}
*/