#include <fstream>
#include <bitset>
#include <vector>
#define MAX 100003
using namespace std;
ifstream fi("ciclueuler.in");
ofstream fo("ciclueuler.out");

int n,m,x,y;
bitset < 5*MAX > viz;      //pentru stergerea muchiilor vizitate
struct muchie {int x,y;} E[5*MAX];//memorarea muchiilor
vector < int > G[MAX],ciclu;

int VerifEulerian(){
     for(int i=1;i<=n;i++)
          if(G[i].size()%2==1)return 0;
     return 1;
}
inline void DF(int nod){     //fara inline la 3 teste crapa stiva?
     for(int i=0;i<G[nod].size();i++)
          if(!viz[G[nod][i]])
            {
                viz[G[nod][i]]=1;
                DF(E[G[nod][i]].x+E[G[nod][i]].y-nod);//(x+y)-x==y
            }
     ciclu.push_back(nod);
}

int main()
{
     fi>>n>>m;
     for(int i=1;i<=m;i++)
     {
          fi>>x>>y;
          G[x].push_back(i); G[y].push_back(i);//memorez indicele muchiei
          E[i].x=x,E[i].y=y;               //memorez muchia cu indicele i
     }
     if(VerifEulerian())
     {
          DF(1);
          for(int i=0;i<ciclu.size();i++)fo<<ciclu[i]<<' ';
          fo<<'\n';
     }
     else fo<<-1<<'\n';
     return 0;
}