#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,rez;
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);
        ++grd[x];
        ++grd[y];
    }
}

void solve ()
{
    vector <int> :: iterator it;
    int i,nod,next;

    for (i=1; i<=n; ++i)
        if (grd[i]&1)
        {
            printf ("-1");
            return ;
        }
    for (st.push (1); !st.empty (); )
    {
        nod=st.top ();
        if (!grd[nod])
        {
            rez.push (nod);
            st.pop ();
        }
        else
        {
            next=g[nod].back ();
            g[nod].PB ();
            st.push (next);
            --grd[nod];
            --grd[next];
            for (it=g[next].begin (); it!=g[next].end (); ++it)
                if (*it==nod)
                {
                    g[next].erase (it);
                    break;
                }
        }
    }
}

void print ()
{
    for ( ; rez.size ()>1; rez.pop ())
        printf ("%d ",rez.top ());
}

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

    read ();
    solve ();
    print ();

    return 0;
}