#include <fstream>
#include <vector>
#define NMAX 100005
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int n,m;
struct nod{int varf,uz;};
vector <nod> g[NMAX];
vector <int> a;
void citire();
void rezolvare();
void dfs(int k);
bool muchie [500005];
int main()
{
    citire();
    rezolvare();
    return 0;
}
void citire()
{
    int i;
    nod a,b;
    a.uz=0;
    b.uz=0;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        a.uz=b.uz=i;
        fin>>a.varf>>b.varf;
        g[a.varf].push_back(b);
        g[b.varf].push_back(a);
    }
}
void rezolvare()
{
    int prim;
    int i;
    for(i=1;i<=n;i++)
    {
        if(g[i].size()%2==0)
        {
            prim=i;
        }
        else
        {
            fout<<-1;
            return;
        }
    }
    dfs(prim);
    for(i=0;i<a.size()-1;i++)
    {
        fout<<a[i]<<' ';
    }
}
void dfs(int k)
{
    int i,j,l;
    for(i=0;i<g[k].size();i++)
    {
        if(muchie[g[k][i].uz]==0)
        {
            muchie[g[k][i].uz]=1;
            l=g[k][i].varf;
            dfs(l);
        }
    }
     a.push_back(k);
}