#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
vector<long long> g[1000005];
vector<bool> vis(1000005, 0);
long long dx[] = {-1, 0, 1, 0};
long long dy[] = {0, -1, 0, 1};
vector<vector<long long> > one, two, three;
vector<long long> st;
void dfs(long long x) {
  st.push_back(x);
  vis[x] = 1;
  for (auto i : g[x]) {
    if (!vis[i]) {
      dfs(i);
    }
  }
}
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, m;
  cin >> n >> m;
  for (long long i = 1; i <= m; ++i) {
    long long x, y;
    cin >> x >> y;
    g[x].push_back(y);
    g[y].push_back(x);
  }
  for (long long i = 1; i <= n; ++i)
    if (!vis[i]) {
      st.clear();
      dfs(i);
      if (st.size() > 3) {
        cout << "-1";
        return 0;
      }
      if (st.size() == 3)
        three.push_back(st);
      else if (st.size() == 2)
        two.push_back(st);
      else
        one.push_back(st);
    }
  if (one.size() < two.size()) {
    cout << "-1";
    return 0;
  }
  vector<vector<long long> > ans;
  while (one.size() > two.size()) {
    vector<long long> x;
    x.push_back(one.back().back());
    one.pop_back();
    x.push_back(one.back().back());
    one.pop_back();
    x.push_back(one.back().back());
    one.pop_back();
    ans.push_back(x);
  }
  for (long long i = 0; i < one.size(); ++i) {
    vector<long long> x;
    x.push_back(one[i][0]);
    x.push_back(two[i][0]);
    x.push_back(two[i][1]);
    ans.push_back(x);
  }
  for (long long i = 0; i < three.size(); ++i) ans.push_back(three[i]);
  for (long long i = 0; i < ans.size(); ++i)
    cout << ans[i][0] << " " << ans[i][1] << " " << ans[i][2] << "\n";
}
