#include <bits/stdc++.h>
using namespace std;
const int nmax=2e5+313;
int gr[nmax],sol[nmax],k,n,m,a,b;
vector <int> v[nmax];
void dfs(int nod)
{
      while(gr[nod])
      {
            int nxt=v[nod][0];
            --gr[nod];
            --gr[nxt];
            v[nod].erase(v[nod].begin());
            v[nxt].erase(find(v[nxt].begin(),v[nxt].end(),nod));
            dfs(nxt);
      }
      sol[++k]=nod;
}
int main()
{
      freopen("ciclueuler.in","r",stdin);
      freopen("ciclueuler.out","w",stdout);
      scanf("%d%d",&n,&m);
      for(int i=1;i<=m;++i)
      {
            scanf("%d%d",&a,&b);
            ++gr[a];
            ++gr[b];
            v[a].push_back(b);
            v[b].push_back(a);
      }
      for(int i=1;i<=n;++i)
      {
            if(gr[i]%2)
            {
                  printf("-1");
                  return 0;
            }
      }
      dfs(1);
      for(int i=1;i<k;++i) printf("%d ",sol[i]);
      return 0;
}