#include <bits/stdc++.h>

using namespace std;

const int NMAX = 1e5+10;
int n,m,was[5 * NMAX];
bool viz[5 * NMAX];
vector < pair < int, int > > v[NMAX];

void dfs(int node){
    viz[node] = 1;
    for(const auto &it: v[node]){
        if(viz[it.first]) continue;
        dfs(it.first);
    }
}

int main(){

    ifstream f("ciclueuler.in");
    ofstream g("ciclueuler.out");
    f >> n >> m;
    for(int i = 1 ; i <= m ; i++){
        int x, y;
        f >> x >> y;
        v[x].push_back({y, i});
        v[y].push_back({x, i});
        was[x]++;
        was[y]++;
    }
    int root;
    for(int i = 1 ; i <= n ; i++){
        if(!was[i]) continue;
        root=i;
        dfs(root);
        break;
    }

    for(int i = 1 ; i <= n ; i++){
        if( (!viz[i] && was[i]) || (v[i].size() & 1) ){
            g << -12;
            return 0;
        }
        viz[i] = 0;
    }

    g << root << " ";
    vector < int > q;
    q.push_back(root);
    while(!q.empty()){
        int node = q.back();

        if(!was[node]){
            if(node != 1)
                g << node << " ";
            q.pop_back();
            continue;
        }

        while(!v[node].empty() && viz[v[node].back().second])
            v[node].pop_back();

        int nxt = v[node].back().first;
        was[nxt]--;
        was[node]--;
        q.push_back(nxt);
        viz[v[node].back().second] = 1;
        v[node].pop_back();
    }

    return 0;
}