#include <fstream>
#include <bitset>
#include <algorithm>
#include <vector>
#define Nmax 100009
#define Mmax 500009
#define pb push_back
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

int N,M,x,y;
bitset < Mmax > viz;
struct edge {int x,y;} E[Mmax];
vector < int > G[Nmax],Cycle;

inline int IsEulerian()
{
     for(int i=1;i<=N;++i)
          if(G[i].size()&1)return 0;
     return 1;
}

inline 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);
     Cycle.pb(node);
}

int main()
{
     f>>N>>M;
     for(int i=1;i<=M;++i)
     {
          f>>x>>y , G[x].push_back(i) , G[y].push_back(i);
          E[i].x=x,E[i].y=y;
     }
     if(IsEulerian())
     {
          DFS(1);
          for(vector< int > ::iterator it=Cycle.begin();it!=Cycle.end();++it)
            g<<*it<<' ';
          g<<'\n';
     }
     else g<<-1<<'\n';
     f.close();g.close();
     return 0;
}