#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int st[1000001],gr[100001],n,m,x,y,nr,c[4000001],k;
struct numar
{
    int x,y;
    bool viz;
}v[500002];
vector <int> a[100005];
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
       v[i].x=x,v[i].y=y;
       a[x].push_back(i);
       a[y].push_back(i);
       gr[x]++;
       gr[y]++;



    }
    for(int i=1;i<=n;i++)
    {
        if(gr[i]%2==1)
        {
            fout<<-1;
            return 0;
        }
    }
    st[++k]=1;
    while(k>=1)
    {
        int nod  = st[k];
         int ok=0;
         while(!a[nod].empty())
         {
             int muchie=a[nod].back();
             a[nod].pop_back();
             if(v[muchie].viz==0)
             {
                 v[muchie].viz=1;
                 x=v[muchie].x;
                 y=v[muchie].y;
                 if(x!=nod)
                    st[++k]=x;
                 else
                    st[++k]=y;
                    ok=1;
                break;

             }
         }
         if(ok==0){
         c[++nr]=nod;
         k--;
         }

    }
    if(nr!=m+1)
    {
        fout<<-1;
        return 0;
    }
    for(int i=1;i<=nr;i++)
        fout<<c[i]<<" ";

    return 0;
}