#include <fstream>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
int n, m, i, j, a, b, start[100001], gr[100001], c[500001], ce[500001], nod, muchie, k1, k2;
vector < pair <int, int> > g[100001];
bool viz[500001];
ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");

int main () {
    fin>>n>>m;
    for (i=1;i<=m;i++) {
        fin>>a>>b;
        gr[a]++;
        gr[b]++;
        g[a].push_back({b,i});
        g[b].push_back({a,i});
    }
    for (i=1;i<=n;i++) {
        if (gr[i]%2!=0) {
            fout<<-1;
            return 0;
        }
    }

    for (i=1;i<=n;i++) {
        if (gr[i]!=0) {
            if (gr[i]%2==0) {
                c[++k1]=i;
                break;
            }
        }
    }

    while (k1!=0)
    {
        int x=c[k1];
        if (gr[x]>0) {
            for (i=start[x];i<g[x].size();i++) {
                nod=g[x][i].first;
                muchie=g[x][i].second;
                if (!viz[muchie]) {
                    start[x]=i+1;
                    viz[muchie]=1;
                    gr[nod]--;
                    gr[x]--;
                    c[++k1]=nod;
                    break;
                }
            }
        } else {
            ce[++k2]=c[k1--];
        }
    }
    if (k2!=m+1) {
        fout<<-1;
        return 0;
    }
    for (i=1;i<k2;i++)
        fout<<ce[i]<<" ";
    return 0;
}