#include <iostream>
#include <stdio.h>
using namespace std;
FILE *f,*g;
struct euler
{
    int nod, urm;
}v[1000002];
int k,n,m;
int start[100002];
int st[1000002];
int deg[100000];
void read()
{   int x,y;
    fscanf(f,"%d %d",&n,&m);
    for(int i=1; i<=m; i++)
    {
        fscanf(f,"%d %d",&x,&y);
        v[++k].nod=y;
        v[k].urm=start[x];
        start[x]=k;
        v[++k].nod=x;
        v[k].urm=start[y];
        start[y]=k;
        deg[x]++;
        deg[y]++;
    }
}
void sterge_muchie(int a, int b)
{
    for(int i=start[a]; i; i=v[i].urm)
        if(v[i].nod==b)
        {
            v[i].nod=-1;
            return;

            }
}
void solve()
{
    for(int i=1; i<=n; i++)
        if(deg[i]%2!=0)
        {
            fprintf(g,"-1");
             return;
        }
    int vf=1,nr,ok;
    st[1]=1;
    while(vf)
    {   ok=0;
        for(int i=start[st[vf]]; i; i=v[i].urm)
        {

            if(v[i].nod!=-1)
            {
                start[st[vf]]=v[i].urm;
                sterge_muchie(v[i].nod,st[vf]);
                ok=1;
                st[++vf]=v[i].nod;
                v[i].nod=-1;
                break;
            }
        }
            if(!ok)
            {
                if(vf>1)
                cout<<st[vf]<<" ";
                fprintf(g,"%d ",st[vf]);
                vf--;
            }
    }
}
int main()
{
    f=fopen("ciclueuler.in","r");
    g=fopen("ciclueuler.out","w");
    read();
  //  for(int i=1; i<=k; i++)
    //    cout<<v[i].nod<<" ";
    //for(int i=1; i<=n; i++)
      //  cout<<start[i]<<" ";
    solve();
    return 0;
}