#include <fstream>
#include <vector>
using namespace std;

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

const int NMAX = 100002, MMAX = 500002;
int n;
bool sters[MMAX];
struct muchie {int x,nr;};
vector<muchie>G[NMAX];
vector<int> C;
muchie m;
void euler(int x)
{
    muchie m;
    while (!G[x].empty())
    {
        m=G[x].back();
        G[x].pop_back();
        if(!sters[m.nr])
        {
            sters[m.nr] = 1;
            euler(m.x);
        }
    }
    C.push_back(x);
}
int main()
{
    int i, nrmuchii, x, y;
    fin>>n>>nrmuchii;
    for (i=1; i<=nrmuchii; i++)
    {
        fin>>x>>y;
        m.x = y; m.nr = i;
        G[x].push_back(m);
        m.x = x;
        G[y].push_back(m);
    }
    for (x=1; x<=n; x++)
        if (G[x].size()%2)
    {
        {
            fout<<-1<<'\n';
            return 0;
        }
    }
    for (x=1; x<=n; x++)
        if(G[x].size())
    {
        euler(x);
        break;
    }
    if (C.size()!=nrmuchii+1)
    {
        fout<<-1<<'\n';
        return 0;
    }
    for (i=0; i<C.size()-1; i++)
        fout<<C[i]<<' ';
    return 0;
}