#include <fstream>
using namespace std;

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

typedef struct nod
{
    int inf,i;
    nod *urm;
} NOD;
typedef NOD *graf[100010];
graf G;

typedef struct queue
{
    int inf;
    queue *previous;
} QUEUE;

QUEUE *q;
int n,m,v[500010],viz[100010],M[100010],x,nr;

void citire()
{
    f>>n>>m;
    for(int i=0;i<m;i++)
    {
        int a,b;
        f>>a>>b;
        NOD *p=new NOD;p->inf=a;p->i=i+1;p->urm=G[b];G[b]=p;
        p=new NOD;p->inf=b;p->i=i+1;p->urm=G[a];G[a]=p;
    }
    f.close();
}

void DF()
{
    q=new QUEUE;q->inf=1;q->previous=NULL;
while(q)
{
    int i=q->inf;
    int ok=1;
    if(!viz[i]){ viz[i]=1;nr++;}
    for(NOD *j=G[i];j&&ok;j=j->urm)
        if(!v[j->i])
        {
            v[j->i]=1;
            QUEUE *p=new QUEUE;
            p->inf=j->inf;
            p->previous=q;q=p;
            ok=0;
        }
    if(ok)
    {
        M[++x]=i;
        QUEUE *aux=q;
        q=q->previous;
        delete aux;
    }
}
}
int main()
{
    citire();
    DF();
    if(x<m||nr<n)
    {
        g<<-1<<'\n';
        return 0;
    }
    for(int i=1;i<=m;i++)
        g<<M[i]<<' ';
    g<<'\n';
    return 0;
}