#include <bits/stdc++.h>
using namespace std;
const int NMAX = 1e5+2;
using pii = pair<int, int>;
int n,m,g[NMAX],st[NMAX],vf;
bool used[NMAX],vis[NMAX];
vector<pii> v[NMAX];
vector<int> cycle;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

int main() {
  fin >> n >> m;
  for(int i = 1; i <= m; i++){
    int x, y;
    fin >> x >> y;
    g[x]++;
    g[y]++;
    v[x].push_back({y, i});
    v[y].push_back({x, i});
  }
  bool ok = true;
  for(int i = 1; i <= n; i++){
    ok &= (g[i]%2 == 0);
  }
  st[++vf] = 1;
  while(vf > 0){
    int nod = st[vf];
    vis[nod] = true;
    if(g[nod] == 0){
      cycle.push_back(nod);
      vf--;
    }else{
      int len = v[nod].size();
      for(int i = len-g[nod]; i < len; i++){
        g[nod]--;
        auto [vecin, idx] = v[nod][i];
        if(used[idx] == false){
          used[idx] = true;
          st[++vf] = vecin;
          break;
        }
      }
    }
  }
  for(int i = 1; i <= n; i++){
    ok &= vis[i];
  }
  if(ok){
    cycle.pop_back();
    for(int it: cycle){
      fout << it << " ";
    }
  }else{
    fout << "-1";
  }
  return 0;
}