# include <fstream>
# include <vector>
# include <deque>
# define DIM1 100010
# define DIM2 500050
# define vecin first
# define poz second
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector<pair<int,int> > Lista[DIM1];
deque<int> q;
int f[DIM2],Marcat[DIM1],d[DIM1],n,m,i,x,y;
void dfs(int nc){
    Marcat[nc]=1;
    for(int i=0;i<Lista[nc].size();i++){
        int nv=Lista[nc][i].vecin;
        if(Marcat[nv]==0)
            dfs(nv);
    }
}
int  main () {
    fin>>n>>m;
    for(i=1;i<=m;i++){
        fin>>x>>y;
        Lista[x].push_back(make_pair(y,i));
        Lista[y].push_back(make_pair(x,i));
        d[x]++;
        d[y]++;
    }
    for(i=1;i<=n;i++)
        if(d[i]){
            dfs(i);
            break;
        }
    for(i=1;i<=n;i++)
        if(d[i]%2==1||(d[i]!=0&&Marcat[i]==0)){
            fout<<"-1\n";
            return 0;
        }
    q.push_back(1);
    while(!q.empty()){
        if(d[q.back()]==0){
            if(q.back()!=1)
                fout<<q.back()<<" ";
            q.pop_back();
            continue;
        }
        int nc=q.back();
        i=Lista[nc].size()-1;
        while(f[Lista[nc][i].poz]==1){
            Lista[nc].pop_back();
            i--;
        }
        int nv=Lista[nc][i].vecin;
        q.push_back(nv);
        d[nc]--;
        d[nv]--;
        f[Lista[nc][i].poz]=1;
    }
    fout<<"1\n";
    return 0;
}