#include <bits/stdc++.h>

using namespace std;

struct EulerWalk {
  int n;
  vector<vector<pair<int, int>>> graph;
  vector<int> cap, walk, buf, deg;

  EulerWalk(int n) : n(n), graph(n + 1), deg(n + 1) {}

  int AddEdge(int a, int b, int c = 1) {
    int ret = cap.size();
    graph[b].emplace_back(a, ret);
    graph[a].emplace_back(b, ret);
    cap.push_back(c);
    deg[a] += c; deg[b] += c;
    return ret;
  }

  void dfs(int node) {
    while (graph[node].size()) {
      int vec, ei; tie(vec, ei) = graph[node].back();
      if (!cap[ei]) graph[node].pop_back();
      else --cap[ei], dfs(vec);
    }
    walk.push_back(node);
  }

  void Go(ostream& cout) {
    for (int i = 0; i < n; ++i) {
      if (deg[i] == 0 || deg[i] % 2) {
        cout << -1 << '\n';
        return;
      }
    }
    dfs(0);
    if (walk.size() <= cap.size()) {
      cout << -1 << '\n';
    } else {
      walk.pop_back();
      for (auto node : walk) 
        cout << node + 1 << " ";
      cout << endl;
    }
  }
};

int main() {
  ifstream cin("ciclueuler.in");
  ofstream cout("ciclueuler.out");
  int n, m; cin >> n >> m;
  EulerWalk E(n);
  for (int i = 0; i < m; ++i) {
    int a, b; cin >> a >> b;
    E.AddEdge(a - 1, b - 1);
  }
  E.Go(cout);
  return 0;
}