#include<stdio.h>
struct muchie
{
    int x,leg;
};
muchie a[1000002];
int n,m,t[100002],stiva[500003],z[500003],vf,x,y,i,k;
int main()
{
    FILE *fin, *fout;
    int rc;
    fin=freopen("ciclueuler.in","r",stdin);
    fout=freopen("ciclueuler.out","w",stdout);
    rc=scanf("%i%i",&n,&m);
    for (k=0,i=1;i<=m;i++)
        {
        rc=scanf("%i%i",&x,&y);
        k++;     a[k].x=y; a[k].leg=t[x]; t[x]=k;
        k++;     a[k].x=x; a[k].leg=t[y]; t[y]=k;
        }
    k=0;
    stiva[1]=1; vf=1;
    while (vf>0)
          {
          x=stiva[vf];
          if (t[x]>0)
             {
             i=t[x];
             y=a[i].x;
             vf++;
             stiva[vf]=y;
             t[x]=a[i].leg;//practic se elimina muchia x y
             i=t[y];
             if (a[i].x==x)t[y]=a[i].leg;
                else {
                     while (a[a[i].leg].x!=x)i=a[i].leg;
                     a[i].leg=a[a[i].leg].leg;
                     }
             }
             else
             {
             k++;
             z[k]=stiva[vf];
             vf--;
             }
          }
    if (k!=m+1 || z[1]!=z[m+1]) { printf("-1");}
       else for (i=1;i<=m;i++)printf("%i ",z[i]);
    fclose(stdout);
    fclose(stdin);
    return 0;
}