#include <bits/stdc++.h>
using namespace std;
ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
const int lim=1e5+4;
const int lim2=5e5+4;
struct Op
{
    int dest;
    int ind;
};
vector<Op> vec[lim];
int tip[lim2];
bool ok[lim];
int deg[lim];
void df(int nod)
{
    ok[nod]=1;
    for(Op x:vec[nod])
    if(!ok[x.dest])
    {
        tip[x.ind]=1;
        df(x.dest);
    }
}
bool used[lim2];
int main()
{
    int n,m,x,y;
    in>>n>>m;
    for(int i=1;i<=m;++i)
    {
        in>>x>>y;
        vec[x].push_back({y,i});
        vec[y].push_back({x,i});
        deg[x]++; deg[y]++;;
    }
    df(1);
    for(int i=1;i<=n;++i)
    {
        if(deg[i]%2!=0 or ok[i]==0)
        {
            out<<-1<<'\n';
            return 0;
        }
    }
    int nod=1;
    for(int i=1;i<=m;++i)
    {
        out<<nod<<' ';
        bool ok=0;
        for(Op x:vec[nod])
        if(tip[x.ind]==0 and !used[x.ind])
        {
            used[x.ind]=1;
            nod=x.dest;
            ok=1;
            break;
        }
        if(ok==1) continue;
        for(Op x:vec[nod])
        if(tip[x.ind]==1 and !used[x.ind])
        {
            used[x.ind]=1;
            nod=x.dest;
            ok=1;
            break;
        }
    }
    out<<'\n';
    return 0;
}