#include <bits/stdc++.h>

using namespace std;

ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

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

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

int main(){
    int i,x,y,node, nxt;
    f >> n >> m;
    for(i = 0 ; i < m ; i++){
        f >> x >> y;
        v[x].push_back({y, i});
        v[y].push_back({x, i});
        was[x]++;
        was[y]++;
    }

    dfs(1);

    for(i = 1 ; i <= n ; i++){
        if( (!viz[i] && was[i]) || was[i] % 2 == 1){
            g << -1;
            return 0;
        }
        viz[i] = 0;
    }

    vector < int > q;
    q.push_back(1);
    g << 1 << " ";
    while(!q.empty()){
        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();

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


    return 0;
}