#include <fstream>
#include <vector>

using namespace std;
ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");
struct muchie{
    int x,y;
    bool anulat;
};
muchie e[500005];
vector <int> a[100005], c;
void euler(int x){
   while(!a[x].empty()){
        int i=a[x].back();
        a[x].pop_back();
        if(e[i].anulat) {
            continue;
        }
        int y=e[i].x+e[i].y-x;
        e[i].anulat=true;
        euler(y);
    }
    c.push_back(x);
}
bool exista(int n){
    for(int i=1;i<=n;i++){
        if(a[i].size()%2!=0){
            return 0;
        }
    }
    return 1;
}
int main()
{
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        cin>>e[i].x>>e[i].y;
        a[e[i].x].push_back(i);
        a[e[i].y].push_back(i);
    }
    if(exista(n)){
        euler(1);
        for(int i=0;i<c.size()-1;i++){
            cout<<c[i]<<" ";
        }
    }
    else{
        cout<<-1;
    }
    return 0;
}