#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;
       else
       {
         euler(1);
         if (C.size()!=m+1) fout << -1;
            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;
    //parcurg lista de adiacenta a lui x de la coada la cap
    while (!G[x].empty())
    {
          nr=G[x].back(); G[x].pop_back();
          //nr este indicele muchiei
          if (M[nr].uz==0)
          {
             M[nr].uz=1; //am sters muchia
             if (M[nr].x==x) y=M[nr].y;
                else y=M[nr].x;
             euler(y);
          }
    }
    C.push_back(x);
}