#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();
        //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);

}