#include <fstream>
#include <vector>
#include <set>

using namespace std;

ifstream cin ("ciclueuler.in");
ofstream cout ("ciclueuler.out");

const int N = 1e5 + 5;

multiset <int> s[N];
vector <int> ans;

void dfs(int nod) {
  while (!s[nod].empty()) {
    auto it = s[nod].begin();
    int vecin = (*it);
    s[nod].erase(it);
    s[vecin].erase(s[vecin].find(nod));
    dfs(vecin);
  }
  ans.push_back(nod);
}

int main()  {
  int n, m, x, y;
  cin >> n >> m;
  for (int i = 1; i <= m; ++i)  {
    cin >> x >> y;
    s[x].insert(y);
    s[y].insert(x);
  }
  dfs(1);
  for (int i = 1; i <= n; ++i)  {
    if (!s[i].empty())  {
      cout << -1 << '\n';
      return 0;
    }
  }
  for (auto it : ans)
    cout << it << ' ';
	return 0;
}