#include<fstream>
#include<vector>
#include<algorithm>
#define Nmax 100009
#define Mmax 500009
#include <bitset>
#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");

int N,M,x,y,sol[2*Nmax];
vector < int > G[Nmax];
vector < pair< int , int> > E;
bitset < Mmax > viz;

void ReadInput()
{
     f>>N>>M;
     for(int i=0;i<M;++i)
          f>>x>>y , G[x].pb(i) ,G[y].pb(i) , E.pb(mp(x,y));
}

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;
}

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

int main()
{
     ReadInput();
     if(IsEulian())
     {
          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;
}