#include <fstream>
#include <vector>
#include <bitset>
#define Nmax 100099
#define Mmax 500099
#define pb push_back
#define x first
#define y second
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

int N,M;
vector < int > G[Mmax],sol;
bitset < Mmax > viz;
typedef pair<int,int> edge;
edge E[Mmax];
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 Euler(int node)
{
     for(vector<int>::iterator it=G[node].begin();it!=G[node].end();++it)
          if(!viz[*it])
          {
               viz[*it]=1;
               Euler(E[*it].x+E[*it].y-node);
          }
     sol.pb(node);
}

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

int main()
{
     ReadInput();
     if(!Eulerian){ g<<"-1\n"; return 0;}
     Euler(1);
     for(vector<int>::iterator it=sol.begin();it!=sol.end();++it)
          g<<*it<<' ';
     g<<'\n';
     return 0;
}