#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;
    ///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 uindicele 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);
}