#include <fstream>
#include <vector>
#define NMAX 100002
#define MMAX 500002

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
struct muchie {int x, y; bool uz;};
int n, m;
muchie M[MMAX];
vector<int> G[NMAX];
vector<int> C;
void citire();
bool grade_pare();
void euler(int x);

int main()
{int i;
 citire();
 if (!grade_pare()) fout<<-1<<'\n';
    else
   {euler(1);
    if (C.size()!=m+1)   fout<<-1<<'\n';
        else
        for (i=0; i<C.size()-1; i++) fout<<C[i]<<' ';
    }
 return 0;
}

void citire()
{int i, x, y;
 fin>>n>>m;
 for (i=1; i<=m; i++)
     {
      fin>>x>>y;
      M[i].x=x; M[i].y=y;
      G[x].push_back(i);
      G[y].push_back(i);
     }
}

bool grade_pare()
{ int i;
  for (i=1; i<=n; i++)
       if (G[i].size()%2) return 0;
  return 1;
}
void euler(int x)
{int nr, y;
 //parcurg lista de adiacenta a lui x de la coada la cap
 while (!G[x].empty())
       {
         nr=G[x].back(); G[x].pop_back();
         //nr este indicele muchiei
         if (M[nr].uz==0)
            {M[nr].uz=1; //am sters muchia
             if (M[nr].x==x) y=M[nr].y;
                else y=M[nr].x;
             euler(y);
            }
       }
   C.push_back(x);
}