#include <stdio.h>
#include <vector>
using namespace std;
FILE *f,*g;

int n,m,q;
int leg[100002],been[500002],sol[500002];
vector <pair<int, int> > v[100002];

void read()
{
  fscanf(f,"%d %d",&n,&m);
  int k=0;
  for(int i=1;i<=m;i++)
  {
    int x,y;
    fscanf(f,"%d %d",&x,&y);

    v[x].push_back({y, i});
    v[y].push_back({x, i});

    leg[x]++,leg[y]++;
  }
}

int OKeuler()
{
    for(int i=1; i<=n; i++)
        if(leg[i]%2==1) return 0;
    return 1;
}

void euler(int nod)
{
    int vec, ind;
    while(v[nod].size()>0)
    {
        vec=v[nod].back().first; ind=v[nod].back().second;
        if(!been[ind])
        {
            been[ind]=1;
            v[nod].pop_back();
            euler(vec);
        }
        else
          v[nod].pop_back();
    }
    sol[++q]=nod;
}
int main()
{
    f=fopen("ciclueuler.in","r");
    g=fopen("ciclueuler.out","w");
    read();
    if(OKeuler())
    {
      euler(1);
      for(int i=1;i<q;i++)
        fprintf(g,"%d ",sol[i]);
    }
    else
      fprintf(g,"-1");
    return 0;
}