#include <fstream>
#include <queue>
#include <bitset>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int i,n,m,ok,nr,nod;
int a[500001],b[500001],d[500001],it;
vector<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();
        while(!v[nod].empty()&&d[v[nod].back()]==1)
            v[nod].pop_back();
        if(v[nod].empty())
        {
            if(ok==1) fout<<nod<<" ";
            ok=1;q.pop_back();continue;
        }
        it=v[nod].back();d[it]=1;
        q.push_back(a[it]+b[it]-nod);
    }
    fin.close();
    fout.close();
    return 0;
}