#include <fstream>
#include <queue>
#include <bitset>
using namespace std;
ifstream fin("date.in");
ofstream fout("date.out");
int i,n,m,ok,nr,nod,vecin,it;
int a[500001],b[500001],d[500001];
deque<int> v[100001],q;

int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>a[i]>>b[i];
        v[a[i]].push_back(i);
        v[b[i]].push_back(i);
    }
    for(i=1;i<=n;i++)
        if(v[i].size()&1)
        {
            fout<<-1;
            return 0;
        }
    q.push_back(1);
    while(!q.empty())
    {
        nod=q.back();nr=0;
        while(!v[nod].empty())
        {
            it=v[nod][0];
            vecin=a[it]+b[it]-nod;
            if(d[it]==0)
            {
                nr++;
                d[it]=1;
                q.push_back(vecin);
                v[nod].pop_front();
                break;
            }
            v[nod].pop_front();
        }
        if(nr==0)
        {
            if(ok==1) fout<<nod<<" ";
            ok=1;q.pop_back();
        }
    }
    fin.close();
    fout.close();
    return 0;
}