#include <bits/stdc++.h>
using namespace std;
const int N = 100;
vector<int> a[N];
bool mark[N] = {false};
vector<vector<int> > ans3, ans2;
vector<int> ans1;
vector<int> h;
int dfs(int v) {
  h.push_back(v);
  int ans = 1;
  mark[v] = true;
  for (int i = 0; i < a[v].size(); i++) {
    if (!mark[a[v][i]]) {
      ans += dfs(a[v][i]);
    }
  }
  return ans;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    u--;
    v--;
    a[v].push_back(u);
    a[u].push_back(v);
  }
  for (int i = 0; i < n; i++) {
    if (!mark[i]) {
      h.clear();
      int tmp = dfs(i);
      if (tmp > 3) {
        cout << -1 << "\n";
        return 0;
      }
      if (tmp == 1)
        ans1.push_back(h[0]);
      else if (tmp == 2)
        ans2.push_back(h);
      else
        ans3.push_back(h);
    }
  }
  if (ans2.size() > ans1.size()) {
    cout << -1 << "\n";
    return 0;
  }
  for (int i = 0; i < ans2.size(); i++) {
    ans2[i].push_back(ans1.back());
    ans1.pop_back();
    ans3.push_back(ans2[i]);
  }
  for (int i = 0; i < ans3.size(); i++) {
    for (int j = 0; j < 3; j++) {
      cout << ans3[i][j] + 1 << " ";
    }
    cout << "\n";
  }
  for (int i = 0; i < ans1.size(); i += 3) {
    cout << ans1[i] + 1 << " " << ans1[i + 1] + 1 << " " << ans1[i + 2] + 1
         << "\n";
  }
  return 0;
}
