#include <stdio.h>
#include <iostream>
#include <stdlib.h>
using namespace std;
FILE*f=fopen("ciclueuler.in","r");
FILE*g=fopen("ciclueuler.out","w");
int k,gr[200005],n,m;
int st[500005];
struct nod{
int inf;
nod *urm;

} *l[100005];
void adaug(nod *&p,int x){
nod *u;
u=new nod;
u->inf=x;
u->urm=p;
p=u;


}
void sterg(nod *&p,int x){
nod *aux,*u;
u=p;
if(u->inf==x) {aux=p;
p=p->urm;
delete aux;
    return;

}
while(u->urm&&u->urm->inf!=x) u=u->urm;
    if(u->urm){
        aux=u->urm;
        u->urm=u->urm->urm;
        delete aux;
    }

}

int caut (nod*u,int x){
nod *p;
for(p=u;p;p=p->urm) if(p->inf==x) return 1;
return 0;
}

int main()
{
fscanf(f,"%d%d",&n,&m);
int i,x,y;
for(i=1;i<=m;i++){
  fscanf(f,"%d%d",&x,&y);
adaug(l[x],y);
adaug(l[y],x);
gr[x]+=1;
gr[y]+=1;

}
for(i=1;i<=n;i++) if(gr[i]%2==1) {
    fprintf(g,"-1");

 return 0;}
for(i=1;i<=n;i++) {
int poz=0;
st[++poz]=1;
while(poz){
    int x=st[poz];
    if(l[x]){
            int w=l[x]->inf;
        st[++poz]=w;
     if(l[w])   sterg(l[w],x);
     if(l[x])   sterg(l[x],w);

    }
    else {fprintf(g,"%d ",st[poz--]);

    k++;
    if(k==m) return 0;

    }

}
}
//cout<<k;
//for(i=1;i<=m;i++) fprintf(g,"%d ",sol[i]);
    return 0;
}