#include <cstdio>
#include <cstring>
#define Nmx 500005

using namespace std;

int n,m,grad[Nmx],st[Nmx],nr;
struct nod
{
    int inf;
    nod *urm;
};
nod *G[Nmx];

void add(int x,int y)
{
    nod *aux=new nod;
    aux->inf = y;
    aux->urm = G[x];
    G[x]=aux;
}

void read()
{
    scanf("%d%d",&n,&m);
    int x,y;
    for(int i=1;i<=m;++i)
    {
        scanf("%d%d",&x,&y);
        grad[x]++;grad[y]++;
        add(x,y);
        add(y,x);
    }
}

void solve()
{
    for(int i=1;i<=n;++i)
        if(grad[i]&1)
        {
            printf("-1\n");
            return ;
        }
    st[++nr]=1;
    while(nr)
    {
        int x=st[nr];
        if(G[x])
        {
            int nd=G[x]->inf;
            G[x]=G[x]->urm;
               st[++nr]=nd;
            if(G[nd])
            {
                if(G[nd]->inf==x)
                    G[nd]=G[nd]->urm;
                else
                for(nod *p=G[nd];p->urm;p=p->urm)
                    if(p->urm->inf==x)
                    {
                        p->urm=p->urm->urm;
                        break;
                    }
            }

        }
        else printf("%d ",st[nr--]);
    }
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    read();
    solve();
    return 0;
}