#include <bits/stdc++.h>
using namespace std;

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

const int MAXN = 1e5 + 5;
const int MAXM = 5 * 1e5 + 5;

int n, m, odd, where = 1;
int x[MAXM], y[MAXM];
vector<int> g[MAXN], r;
bool vis[MAXM];

inline void euler(const int node) {
  for (const auto i : g[node]) {
    if (!vis[i]) {
      vis[i] = true;
      euler(x[i] + y[i] - node);
    }
  }
  r.push_back(node);
}

int main() {
  fin >> n >> m;
  for (int i = 1; i <= m; ++i) {
    fin >> x[i] >> y[i];
    g[x[i]].push_back(i);
    g[y[i]].push_back(i);
  }
  for (int i = 1; i <= n; ++i) {
    odd += g[i].size() % 2;
    if (g[i].size() % 2 == 1) {
      where = i;
    }
  }
  if (odd != 0 && odd != 2) {
    fout << "-1\n";
  } else {
    euler(where);
  }
  for (const auto i : r) {
    fout << i << ' ';
  }
  fout.close();
  return 0;
}