#include <bits/stdc++.h>
#define ll long long
#define all(a) (a).begin(), (a).end()
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define sz() size()
#define fr first
#define sc second
#define pb push_back
#define er erase
#define in insert
#define pi pair<int,int>
#define pii pair<pair<int,int>,int>
#define mp make_pair
#define int long long
#define rc(s) return cout<<s,0
#define rcc(s) cout<<s,exit(0)
///#define cin fin
///#define cout fout
using namespace std;

const int mod=1e9+7;
const int mod1=998244353;

       ifstream fin("ciclueuler.in");
    ofstream fout("ciclueuler.out");

int n,m,x,y;
vector<int>ans;
vector<int>nod[100005];
pair<pair<int,int>,int>edge[500005];

int32_t main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    fin >> n >> m;
    for(int i=1;i<=m;i++){
        fin >> x >> y;
        edge[i]={{x,y},1};
        nod[x].push_back(i);
        nod[y].push_back(i);
    }
    for(int i=1;i<=n;i++) if(nod[i].size()%2==1) {fout << -1; return 0;}
    vector<int>st;
    st.push_back(1);
    while(!st.empty()){
        int node=st.back();
        if(nod[node].size()){
            int g=nod[node].back();
            if(edge[g].sc==1){
                edge[g].sc=0;
                nod[node].pop_back();
                st.push_back(edge[g].fr.fr+edge[g].fr.sc-node);
                continue;
            }
            else nod[node].pop_back();
        }
        else{
            st.pop_back();
            ans.push_back(node);
        }
    }
    ans.pop_back();
    for(int i=0;i<ans.size();i++) fout << ans[i] << ' ';
}