#include <fstream>
#include<vector>
#define Dmax 100005
using namespace std;

ifstream intrare("ciclueuler.in");
ofstream iesire("ciclueuler.out");

int n, m;
int d[Dmax];
int viz[Dmax];
vector<int>G[Dmax];
int total;

struct nod{int vf; struct nod * urm;};
typedef struct nod * Lista;

Lista C1, C2, sfC1, sfC2;

void citire();
void dfs(int x);
void determinare_eulerian();
bool conex();
bool gradepare();
int ciclu(int x, Lista &inc, Lista &sf);
void afisare();

int main()
{
  citire();
  if (conex() && gradepare())
  {
    determinare_eulerian();
    afisare();
  }
  else
    iesire <<-1<<'\n';
  iesire.close();
  return 0;
}
void citire()
{
    int x, y, i;
    intrare>>n>>m;
    for(i=1;i<=m;i++)
    {
        intrare>>x>>y;
        d[x]++; d[y]++;
        G[x].push_back(y);
        G[y].push_back(x);
    }
}
void dfs(int x)
{
    int i;
    viz[x]=true;
    for(i=0;i<G[x].size();i++)
        if(!viz[G[x][i]])
            dfs(G[x][i]);
}
bool gradepare()
{
  int i;
  for(i = 1; i <= n; i++)
    if (d[i] % 2)
      return 0;
  return 1;
}

bool conex()
{
  int x, i;
  for(x = 1; x <= n && !d[x]; x++);
    if (x >= n)
      return 0;
    dfs(x);
    for(i = 1; i <=n; i++)
      if (!viz[i] && d[i])
        return 0;
    return 1;
}

void determinare_eulerian()
{
  int x, nr2;
  Lista p, q;
  for(x = 1; x <= n && !d[x]; x++);
  total = ciclu(x,C1,sfC1);
  while(total != m)
  {
    for(p = C1; !d[p->vf]; p = p -> urm);
    nr2 = ciclu(p->vf,C2,sfC2);
    q = p -> urm;
    p->urm = C2->urm;
    sfC2->urm = q;
    total += nr2;
  }
}

int ciclu(int x, Lista &inc, Lista &sf)
{
  Lista p;
  int y, uvf, i,j,lg = 0; 
  p = new nod;
  p->vf = x;
  p->urm = NULL;
  inc = sf = p;
  do
  {
    uvf = sf->vf;
    for(i=0; i<G[uvf].size();i++)
        if(G[uvf][i])
            break;
    y=G[uvf][i];
    p = new nod;
    p->vf = y;
    p->urm = NULL;
    sf->urm = p;
    sf = p;
    lg++; 
    G[uvf][i]=0;
    for(j=0;j<G[y].size();j++)
        if(G[y][j]==uvf)
        {
            G[y][j]=0;
            break;
        }
    d[uvf]--; d[y]--;
  }while(y != x);
  return lg;
} 
void afisare()
{
    Lista p;
    for(p=C1; p;p=p->urm)
        iesire<<p->vf<<' ';
    iesire<<'\n';
}