#include <algorithm>
#include <vector>
#include <stack>
using namespace std;

#define pb push_back
#define PB pop_back
#define DIM 100005

vector <int> g[DIM];
stack <int> st;
bool viz[DIM];
int grd[DIM];
int n,m;

void read ()
{
    int i,x,y;

    scanf ("%d%d",&n,&m);
    for (i=1; i<=m; ++i)
    {
        scanf ("%d%d",&x,&y);
        g[x].pb (y);
        g[y].pb (x);
    }
}

void df (int nod)
{
    vector <int> :: iterator it;

    viz[nod]=1;
    for (it=g[nod].begin (); it!=g[nod].end (); ++it)
        if (!viz[*it])
            df (*it);
}

int eulerian ()
{
    int i;

    df (1);
    for (i=1; i<=n; ++i)
        if (!viz[i] || (int)(g[i].size ())%2)
            return 0;
    return 1;
}

void solve ()
{
    vector <int> :: iterator it;
    int nod,newnod,first;

    first=0;
    for (st.push (1); !st.empty (); )
    {
        nod=st.top ();
        if (g[nod].empty ())
        {
            if (first)
                printf ("%d ",nod);
            st.pop ();
            first=1;
        }
        else
        {
            newnod=g[nod].back ();
            st.push (newnod);
            g[nod].PB ();
            for (it=g[newnod].begin (); it!=g[newnod].end (); ++it)
                if (*it==nod)
                {
                    g[newnod].erase (it);
                    break ;
                }
        }
    }
}

int main ()
{
    freopen ("ciclueuler.in","r",stdin);
    freopen ("ciclueuler.out","w",stdout);

    read ();
    if (eulerian ())
        solve ();
    else
        printf ("-1");

    return 0;
}