#include <fstream>
#include <vector>
#include <bitset>
#include <stack>

using namespace std;
const int NMAX = 100001, MMAX = 500001;

struct muchie
{
    int nod, nrm;
    muchie(int xx = 0, int nn = 0): nod(xx), nrm(nn) {}
};

int n, m;

vector<muchie> G[NMAX];
vector<int> L;
bitset<MMAX>elim;
stack<int >S;

ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

void citire()
{
    int x, y;
    f >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        f >> x >> y;
        G[x].push_back(muchie(y, i));
        G[y].push_back(muchie(x, i));
    }
}

void euler()
{
    int x;
    muchie mm;
    S.push(1);
    while(!S.empty())
    {
       x=S.top();
       if(G[x].size()>0)
       {
           mm=G[x].back();
           G[x].pop_back();
           if(!elim[mm.nrm])
           {
               elim[mm.nrm]=1;
               S.push(mm.nod);
           }
       }
           else
           {
               L.push_back(x);
               S.pop();
           }


}

}


int main()
{
    bool ok = 1;
    citire();
    for(int i = 1; i <= n && ok; i++)
{
    if(G[i].size() & 1)
            ok = 0;
    }
    if(ok)
{
    euler();
        for(int i = L.size() - 1; i >= 1; i--)
            g << L[i] << ' ';
    }
    else g << "-1\n";
        f.close();
        g.close();
        return 0;
    }