#include <bits/stdc++.h>
using namespace std;
string sum(string a, string b) {
  int k;
  if (a.size() > b.size()) {
    k = a.size() - b.size();
    for (int i = 0; i < k; i++) {
      b.insert(0, "0");
    }
  } else {
    k = b.size() - a.size();
    for (int i = 0; i < k; i++) {
      a.insert(0, "0");
    }
  }
  vector<int> vect;
  vect.clear();
  int qw = 0;
  for (int i = a.size() - 1; i >= 0; i--) {
    vect.push_back((a[i] - '0') + (b[i] - '0'));
  }
  for (int i = 0; i < vect.size(); i++) {
    if (vect[i] > 9) {
      if (i == vect.size() - 1) {
        vect.push_back(vect[i] / 10);
        vect[i] %= 10;
        break;
      }
      vect[i + 1] += (vect[i] / 10);
      vect[i] %= 10;
    }
  }
  string res;
  res.resize(vect.size());
  for (int i = 0; i < vect.size(); i++) {
    res[i] = (vect[i] + '0');
  }
  res = string(res.rbegin(), res.rend());
  return res;
}
int main() {
  int n, m;
  while (cin >> n >> m) {
    vector<int> v[2];
    v[0].resize(m);
    v[1].resize(m);
    for (int i = 0; i < m; i++) {
      cin >> v[0][i] >> v[1][i];
    }
    vector<int> stud[1005];
    int z = 0;
    for (int i = 0; i < m; i++) {
      bool f = false;
      for (int p = 0; p < n / 3; p++) {
        for (int k = 0; k < stud[p].size(); k++) {
          if (v[0][i] == stud[p][k]) {
            stud[p].push_back(v[1][i]);
            f = true;
            break;
          } else if (v[1][i] == stud[p][k]) {
            stud[p].push_back(v[0][i]);
            f = true;
            break;
          }
        }
      }
      if (!f) {
        stud[z].push_back(v[0][i]);
        stud[z].push_back(v[1][i]);
        z++;
      }
    }
    for (int i = 0; i < n / 3; i++) {
      for (int p = 0; p < stud[i].size(); p++) {
        for (int u = 0; u < stud[i].size(); u++) {
          if (p != u && stud[i][p] == stud[i][u]) {
            stud[i].erase(stud[i].begin() + u);
            u--;
          }
        }
      }
    }
    vector<int> vect;
    for (int i = 1; i <= n; i++) {
      vect.push_back(i);
    }
    for (int i = 0; i < m; i++) {
      for (int p = 0; p < vect.size(); p++) {
        if (v[0][i] == vect[p]) {
          vect.erase(vect.begin() + p);
          p--;
        } else if (v[1][i] == vect[p]) {
          vect.erase(vect.begin() + p);
          p--;
        }
      }
    }
    for (int i = 0; i < vect.size(); i++) {
      for (int p = 0; p < n / 3; p++) {
        if (stud[p].size() != 3) {
          stud[p].push_back(vect[i]);
          break;
        }
      }
    }
    for (int i = 0; i < n / 3; i++) {
      for (int p = 0; p < stud[i].size(); p++) {
        for (int u = 0; u < stud[i].size(); u++) {
          if (p != u && stud[i][p] == stud[i][u]) {
            stud[i].erase(stud[i].begin() + u);
            u--;
          }
        }
      }
    }
    bool f = true;
    for (int i = 0; i < n / 3; i++) {
      if (stud[i].size() != 3) {
        f = false;
      }
    }
    if (f) {
      for (int i = 0; i < n / 3; i++) {
        for (int p = 0; p < stud[i].size() - 1; p++) {
          cout << stud[i][p] << " ";
        }
        cout << stud[i][stud[i].size() - 1] << endl;
      }
    } else {
      cout << "-1" << endl;
    }
  }
  return 0;
}
