#include <iostream>
#include <fstream>
#include <vector>
#define NMAX 100005
#define MMAX 500005
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector <int> g[NMAX];
vector <int> stiva,ciclu;
bool used[MMAX];
int A[MMAX],B[MMAX],n,m;
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++) {
        int a,b;
        fin>>a>>b;
        g[a].push_back(i);
        g[b].push_back(i);
        A[i]=a;
        B[i]=b;
    }
    for(int i=1;i<=n;i++) {
        if(g[i].size()%2==1) {
            fout<<-1;
            return 0;
        }
    }
    stiva.push_back(1);
    while(!stiva.empty()) {
        int nod=stiva.back();
        if(!g[nod].empty()) {
            int edge=g[nod].back();
            g[nod].pop_back();
            if(!used[edge]) {
                used[edge]=true;
                int next=A[edge];
                if(next==nod)
                    next=B[edge];
                stiva.push_back(next);
            }
        } else {
            stiva.pop_back();
            ciclu.push_back(nod);
        }
    }
    for(int i=0;i<ciclu.size()-1;i++)
        fout<<ciclu[i]<<" ";
    return 0;
}