#include <fstream>
#include <list>
#include <vector>
#define pb push_back
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
vector <int> a[1001];
list <int> q;
int n,m,i,x,y;
void euler (int x)
{
    int nr=0;
    vector <int> :: iterator it;
    q.pb(x);
    while (!q.empty())
    {
        x=q.front();
        if (a[x].empty())
        {
            q.pop_front();
            if (nr<m) g<<x<<' ';
            nr++;
        }
        else
        {
          int i=a[x].back();
          q.push_front(a[x].back());
          a[x].pop_back();
            for (it=a[i].begin();it!=a[i].end();it++)
              if (*it==x) {a[i].erase(it); break;}
        }
    }
}
int main()
{
  f>>n>>m;
  for (i=1;i<=m;i++)
  {
      f>>x>>y;
      a[x].pb(y);
      a[y].pb(x);
  }
for (i=1;i<=n;i++)
if (a[i].size()%2!=0) { g<<"-1"; return 0;}
  euler(1);
return 0;
}