#include <fstream>
#include <vector>
#include <algorithm>
#include <stack>
using namespace std;
ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");
vector <int> V[100013];
stack <int> St;
int n,m,i,x,y;
inline bool verify()
{   
 for(int i=1;i<=n;i++)
    if(V[i].size()%2) return 0;
    return 1;
}
int main()
{
 cin>>n>>m;
 for (i=1;i<=m;++i){
            cin>>x>>y;
            V[x].push_back(y);
            V[y].push_back(x);
            }
 if(!verify()) cout<<-1;
    else {
          St.push(1);
          int p;
          int virf;
          while(!St.empty()){
                   if(V[St.top()].size() && St.size()<=m){
                                                      p=V[St.top()].back();
                                                      virf=St.top();
                                                      V[virf].pop_back();
                                                      St.push(p);
                                                      V[p].erase(find(V[p].begin(),V[p].end(),virf));
                                                      }
                                                  else{   
                                                       if(St.size()>1) cout<<St.top()<<" ";
                                                       St.pop();
                                                       if(!St.size()) break;
                                                       }
                          }
          }
 return 0;
}