#include <fstream>
#include<vector>
#define NMAX 100002
#define MMAX 500002
using namespace std;
ifstream fin("cicliueuler.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;
//parcurg lista de adiacenta a lui x de la coada ka cap
while(!G[x].empty())
{
    nr=G[x].back();G[x].pop_back();
    //nr este indcele 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);
}
}