#include <fstream>
#include <deque>
#include <vector>
#define N 100010
#define M 500010
using namespace std;
deque <int> w;
vector <int> v[N];
vector <int>::iterator it;
int viz[M],a[M],b[M],aux,i,n,m,gr[N],q[M],c[M];
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
void go(int nod)
{
    if(m){fout<<nod<<' ';m--;}
    else
        return;
    while(c[nod])
    {
        m--;
        c[nod]--;
        fout<<nod<<' ';
    }
    if(!m)return;
    while(v[nod].size())
    {
        int muchie=v[nod].back();
        if(viz[muchie]){v[nod].pop_back();continue;}
        viz[muchie]=1;
        v[nod].pop_back();
        go(a[muchie]+b[muchie]-nod);
    }
}
int main()
{
//    freopen("ciclueuler.in","r",stdin);
//    freopen("ciclueuler.out","w",stdout);
    //scanf("%d%d",&n,&m);
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        //scanf("%d%d",&a[i],&b[i]);
        fin>>a[i]>>b[i];
        if(a[i]==b[i]){c[a[i]]++;continue;}
        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");
           fout<<"-1";
            return 0;
        }
    viz[1]=1;
      viz[1]=1;
    w.push_back(1);
    while(w.size())
    {
        int x=w.front();
        w.pop_front();
        for(it=v[x].begin();it!=v[x].end();it++)
        {
            int vec=a[*it]+b[*it]-x;
            if(!viz[vec])
            {
                viz[vec]=1;
                q[*it]=1;
                w.push_back(vec);
            }
    }
    }
    for(i=1;i<=n;i++)
    {
        if(!viz[i])
        {
            fout<<"-1";
            return 0;
        }
        viz[i]=0;
    }
    for(i=1;i<=n;i++)
    {
        int L,R;L=0;R=v[i].size()-1;
        do
        {
            while(L<R&&q[v[i][L]])L++;
            while(L<R&&!q[v[i][R]])R--;
            if(L<R){aux=v[i][L];v[i][L]=v[i][R];v[i][R]=aux;L++,R--;}

        }while(L<R);
    }
    go(1);
    return 0;
}