#include <bits/stdc++.h>
using namespace std;
long long n, t = 1, c1, c2;
vector<vector<long long>> adj;
vector<vector<long long>> g;
vector<bool> visited;
void DFS(long long v) {
  visited[v] = true;
  g[t].push_back(v);
  for (auto i : adj[v])
    if (!visited[i]) DFS(i);
}
long long number_of_components() {
  for (long long v = 1; v <= n; v++)
    if (!visited[v]) {
      DFS(v);
      if (g[t].size() > 3) {
        cout << "-1";
        return -1;
      }
      if (g[t].size() == 1) c1++;
      if (g[t].size() == 2) c2++;
      t++;
    }
}
void solve() {
  long long m, x, y, j = 0, h = 1;
  cin >> n >> m;
  adj.resize(n + 1);
  g.resize(n + 1);
  visited.assign(n + 1, false);
  for (long long i = 1; i <= m; i++) {
    cin >> x >> y;
    adj[x].push_back(y);
    adj[y].push_back(x);
  }
  long long z = number_of_components();
  if (z == -1) return;
  if (c2 > c1) {
    cout << "-1";
    return;
  }
  if ((c1 - c2) % 3 != 0) {
    cout << -1;
    return;
  }
  for (long long i = 1; i <= t; i++) {
    if (g[i].size() == 3) {
      for (auto v : g[i]) cout << v << " ";
      cout << "\n";
    }
    if (g[i].size() == 2) {
      for (auto v : g[i]) cout << v << " ";
      for (j = h; j <= t; j++)
        if (g[j].size() == 1) {
          cout << g[j][0];
          break;
        }
      h = j + 1;
      cout << "\n";
    }
  }
  for (long long i = j + 1; i <= t; i++) {
    if (g[i].size() == 1) cout << g[i][0] << " ";
    if ((j - i) % 3 == 0) cout << "\n";
  }
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
  cerr << "time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs" << endl;
  return 0;
}
