#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

const int MAXN = 1e5 + 1,MAXM = 5e5 + 1;

using namespace std;

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

stack<int>graf[MAXN];
bool viz[MAXM];
int n,m,from[MAXM],to[MAXM];
int ans[MAXM];

int main()
{
    in.tie(0);
    out.tie(0);
    ios::sync_with_stdio(false);

    in>>n>>m;
    for(int i = 1; i <= m; i++){
        int x,y;
        in>>x>>y;
        graf[x].push(i);
        graf[y].push(i);
        from[i] = x;
        to[i] = y;
    }
    for(int i = 1; i <= n; i++){
        if(graf[i].size() & 1){
            out<<-1;
            return 0;
        }
    }
    stack<int>stiva;
    stiva.push(1);
    int index = 0;
    while(stiva.size()){
        int nod = stiva.top();
        if(graf[nod].size() > 0){
            int label = graf[nod].top();
            graf[nod].pop();
            /// am label-ul muchiilor
            if(!viz[label]){
                int vecin = from[label] ^ to[label] ^ nod;
                viz[label] = true;
                stiva.push(vecin);
            }
        }else{
            ans[index++] = nod;
            stiva.pop();
        }
    }
//    for(int i = 1; i <= m; i++){
//        if(!viz[i]){
//            out<<-1;
//            return 0;
//        }
    for(int i = 0; i < index - 1; i++)
        out<<ans[i]<<' ';
    return 0;
}