#include <bits/stdc++.h>
using namespace std;
int INF = 0x3f3f3f3f;
const double EPS = 1e-6;
long long MOD = 1000000007;
int static_init_function() {
  cout.sync_with_stdio(false);
  return 0;
}
int main(void) {
  int n;
  cin >> n;
  int m;
  cin >> m;
  vector<pair<int, int> > v;
  for (int i = 0; i < m; ++i) {
    pair<int, int> temp;
    cin >> temp.first >> temp.second;
    v.push_back(temp);
  }
  vector<int> p(n);
  vector<int> cnt(n);
  for (int i = 0; i < n; ++i) {
    p[i] = i;
    cnt[i] = 1;
  }
  for (int i = 0; i < m; ++i) {
    int s = p[v[i].second - 1];
    int f = p[v[i].first - 1];
    for (int j = 0; j < n; ++j) {
      if (p[j] == s) {
        p[j] = f;
        cnt[f]++;
        cnt[s]--;
      }
    }
  }
  for (int i = 0; i < n; ++i) {
    if (cnt[i] > 3) {
      cout << -1;
      return 0;
    }
  }
  for (int i = 0; i < n; ++i) {
    if (cnt[i] == 2) {
      int j = 0;
      for (; j < n; ++j) {
        if (cnt[j] == 1) {
          p[j] = p[i];
          cnt[j]--;
          cnt[i]++;
          break;
        }
      }
      if (j == n) {
        cout << -1;
        return 0;
      }
    }
  }
  for (int i = 0; i < n; ++i) {
    if (cnt[i] == 3) {
      for (int j = 0; j < n; ++j) {
        if (p[j] == p[i]) cout << j + 1 << " ";
      }
      cout << endl;
    }
  }
  int ones = 0;
  for (int i = 0; i < n; ++i) {
    if (cnt[i] == 1) {
      cout << i + 1 << " ";
      ones = (ones + 1) % 3;
      if (ones == 0) cout << endl;
    }
  }
}
