#include<fstream>
#include<vector>
#include<stack>
#include<bitset>
using namespace std;
#define NMAX 100005
#define MMAX 500005
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector < pair <int,int> > v[NMAX];
vector < pair <int,int> >::reverse_iterator it;
stack <int> st;
bitset <MMAX> viz;
bitset <NMAX> L;
int n,m,x,y,D[NMAX];
bool ok;
void dfs(int nod)
{
    int i;
    L[nod]=1;
    for (i=0;i<v[nod].size();++i)
        if (!L[v[nod][i].first])
            dfs(v[nod][i].first);
}
int main()
{
    int i;
    fin>>n>>m;
    for (i=1;i<=m;++i)
    {
        fin>>x>>y;
        v[x].push_back(make_pair(y,i));
        v[y].push_back(make_pair(x,i));
        ++D[x], ++D[y];
    }
    dfs(1);
    for (i=1;i<=n;++i)
        if (!L[i] || D[i]&1)
        {
            fout<<"-1\n";
            return 0;
        }
    st.push(1);
    while (!st.empty())
    {
        x=st.top();
        for (it=v[x].rbegin();it!=v[x].rend();++it)
            if (viz[it->second])
                v[x].pop_back();
            else
                break;
        if (it!=v[x].rend())
        {
            viz[it->second]=1;
            st.push(it->first);
            v[x].pop_back();
        }
        else
        {
            if (ok)
                fout<<x<<" ";
            else
                ok=true;
            st.pop();
        }
    }
    fout<<"\n";
    return 0;
}