// Graf Eulerian - O ( )
// Un graf este eulerian daca este conex si orice nod are grad par
#include <fstream>
#include <vector>
#include <bitset>
#define Nmax 100150
#define Mmax 500150
#define pb push_back
#define mp make_pair
#define x first
#define y second
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
typedef pair<int,int> edge;
int N,M,sol[Mmax];
vector <int> G[Nmax];
edge E[Mmax];
bitset < Mmax > viz;

inline void ReadInput()
{
     f>>N>>M;
     for(int i=1;i<=M;++i)
          f>>E[i].x>>E[i].y , G[E[i].x].pb(i) , G[E[i].y].pb(i);

}

void DFS(int node)
{
     for(vector<int>::iterator it=G[node].begin();it!=G[node].end();++it)
          if(!viz[*it])
          {
               viz[*it]=1;
               DFS(E[*it].x+E[*it].y-node);
     sol[++sol[0]]=node;
          }
}

inline bool  Eulerian()
{
     for(int i=1;i<=N;++i)
          if( (int)G[i].size() % 2==1)return 0;
     return 1;
}

int main()
{
     ReadInput();
     if(Eulerian())
     {
          DFS(1);
          for(int i=1;i<=sol[0];++i)g<<sol[i]<<' ';
          g<<'\n';
     }
     else g<<-1<<'\n';
     f.close();g.close();
     return 0;
}