#include<fstream>
#include<vector>

using namespace std;

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

int n,m,x,y,i,nod2,ok;
vector<int> a[100001],Q;
vector<int>::iterator it2,it3;

void euler(int nod)
{
    while (a[nod].size())
    {
        nod2=a[nod].back();
        for (it2=a[nod2].begin();it2!=a[nod2].end();it2++)
            if (*(it2)==nod)
            {
                a[nod2].erase(it2);
                break;
            }
        a[nod].pop_back();
        euler(nod2);
    }
    Q.push_back(nod);
}

int main()
{
    in>>n>>m;
    for (i=1;i<=m;i++)
    {
        in>>x>>y;
        a[x].push_back(y);
        a[y].push_back(x);
    }
    for (i=1;i<=n;i++)
        if (a[i].size()%2) ok=1;
    euler(1);
    if (ok) out<<"-1\n";
        else
        {
            for (i=0;i<Q.size();i++)
                out<<Q[i]<<' ';
        }
}