#include <iostream>
#include <fstream>
#include <vector>
#define nmax 100002
#define mmax 500002


using namespace std;

ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");
struct muchie {int x,y; bool uz;};
int n,m;
muchie M[mmax];
vector<int> G[nmax];
vector<int> C;

void citire();
bool grade_pare();
void euler (int x);

int main()
{
    int i;
    citire();
    if (!grade_pare()) fout<<-1<<'\n';
    else
    {
    euler(1);
    if(C.size()!=m+1) fout<<-1<<'\n';
    else
      for (i=0;i<C.size()-1;i++) fout<<C[i]<<' ';
    }
    return 0;
}

void citire()
{
  int i,x,y;
  fin>>n>>m;
  for (i=1;i<=m;i++)
  {
    fin>>x>>y;
    M[i].x=x;
    M[i].y=y;
    G[x].push_back(i);
    G[y].push_back(i);
  }
}

bool grade_pare()
{
  int i;
  for (i=1;i<=n;i++)
    if (G[i].size()%2) return 0;
  return 1;
}

void euler (int x)
{
  int nr,y;
  while (!G[x].empty())
  {
    nr=G[x].back();
    G[x].pop_back();
    if (M[nr].uz==0)
    {
      M[nr].uz=1;
      if (M[nr].x==x) y=M[nr].y;
      else
        y=M[nr].x;
      euler(y);
    }
  }
  C.push_back(x);
}