#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const int N = 2e5 + 5;
const long long inf = 1e18 + 5;
bool sortbysec(const pair<pair<long long, long long>, long long> &a,
               const pair<pair<long long, long long>, long long> &b) {
  return (a.second > b.second);
}
long long powermod(long long x, long long y, long long p) {
  long long res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
bool isprime(int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (int i = 5; i * i <= n; i = i + 6)
    if (n % i == 0 || n % (i + 2) == 0) return false;
  return true;
}
long long f;
vector<long long> adj[N];
vector<long long> vis(N);
long long depth[N];
long long deg[N];
long long sz;
void dfs(long long x, vector<long long> &a) {
  a.push_back(x);
  vis[x] = 1;
  sz++;
  for (auto e : adj[x]) {
    if (vis[e]) continue;
    vis[e] = 1;
    dfs(e, a);
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long n, m;
  cin >> n >> m;
  for (long long i = 0; i < m; i++) {
    long long x, y;
    cin >> x >> y;
    adj[x].push_back(y);
    adj[y].push_back(x);
    deg[x]++;
    deg[y]++;
    if (deg[x] > 3 || deg[y] > 3) {
      cout << -1;
      return 0;
    }
  }
  vector<vector<long long>> ans;
  for (int i = 1; i <= n; i++) {
    if (!vis[i]) {
      sz = 0;
      vector<long long> a;
      dfs(i, a);
      if (sz > 3) {
        cout << -1 << "\n";
        return 0;
      }
      ans.push_back(a);
    }
  }
  vector<long long> one;
  vector<pair<long long, long long>> two;
  for (long long i = 0; i < ans.size(); i++) {
    if (ans[i].size() == 1) {
      one.push_back(ans[i][0]);
      ans.erase(ans.begin() + i);
      i--;
    } else if (ans[i].size() == 2) {
      two.push_back({ans[i][0], ans[i][1]});
      ans.erase(ans.begin() + i);
      i--;
    }
  }
  if (one.size() < two.size() || (one.size() - two.size()) % 3 != 0) {
    cout << -1;
    return 0;
  }
  long long i;
  for (i = 0; i < two.size(); i++) {
    vector<long long> x;
    x.push_back(one[i]);
    x.push_back(two[i].first);
    x.push_back(two[i].second);
    ans.push_back(x);
  }
  vector<long long> x;
  for (; i < one.size(); i++) {
    x.push_back(one[i]);
    if (x.size() == 3) {
      ans.push_back(x);
      x.clear();
    }
  }
  for (long long i = 0; i < ans.size(); i++) {
    cout << ans[i][0] << " " << ans[i][1] << " " << ans[i][2] << "\n";
  }
  return 0;
}
