#include <cstdio>
#include <vector>
#define N 100010
#define M 200010

using namespace std;
vector< int >v[N];
int n,m,i,a[M],b[M],gr[N],viz[N];
void df(int),go(int);
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        scanf("%d%d",&a[i],&b[i]);
        v[a[i]].push_back(i);
        v[b[i]].push_back(i);
        gr[a[i]]++;gr[b[i]]++;
    }
    for(i=1;i<=n;i++)
        if(gr[i]&1)
        {
            printf("-1\n");
            return 0;
        }
    df(1);
    for(i=1;i<=n;i++)
        if(!viz[i])
        {
            printf("-1\n");
            return 0;
        }
    go(1);
    return 0;
}
void df(int nod)
{
    viz[nod]=1;
    for(vector<int>::iterator it=v[nod].begin();it!=v[nod].end();it++)
    {
        if(viz[a[*it]+b[*it]-nod])continue;
        else
        {
            int aux=*it;
            *it=v[nod][0];
            v[nod][0]=aux;
            df(a[aux]+b[aux]-nod);
        }
    }
}
void go(int nod)
{
    if(m){ printf("%d ",nod); m--; }
    while(v[nod].size()&&!a[v[nod].back()])v[nod].pop_back();
    if(v[nod].size())
    {

        int muchie=v[nod].back();
        int vec=a[muchie]+b[muchie]-nod;a[muchie]=0;
        v[nod].pop_back();
        go(vec);

    }

}