#include <fstream>
#include <vector>
#define NMAX 100002
#define MMAX 500002

using namespace std;

ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");

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

struct muchie {int x,y; bool uz;};
int n, m;
muchie M[NMAX];
vector <int> G[NMAX];
vector <int> C;

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);
}