#include <bits/stdc++.h>
using namespace std;
const long double PI = 3.14159265359;
const long long MOD = (long long)998244353ll;
const long long MAXN = (long long)480 + 10;
const long long INF = (long long)9223372036854775;
const long double EPS = (long double)1e-8;
long long mark[MAXN];
vector<long long> coms[MAXN / 3];
vector<vector<long long> > three, two, one;
vector<long long> g[MAXN];
void DFS(long long node, long long c) {
  mark[node] = 1;
  coms[c].push_back(node);
  for (auto adj : g[node]) {
    if (!mark[adj]) DFS(adj, c);
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n, m;
  cin >> n >> m;
  long long u, v;
  for (int i = 0; i < m; i++) {
    cin >> u >> v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  long long com = 0;
  for (int i = 1; i <= n; i++) {
    if (!mark[i]) {
      DFS(i, com);
      if (coms[com].size() > 3) return cout << -1, 0;
      if (coms[com].size() == 3) three.push_back(coms[com]);
      if (coms[com].size() == 2) two.push_back(coms[com]);
      if (coms[com].size() == 1) one.push_back(coms[com]);
      com++;
    }
  }
  if (two.size() > one.size()) return cout << -1, 0;
  for (auto x : three) {
    for (auto y : x) cout << y << " ";
    cout << '\n';
  }
  long long p = 0;
  for (auto x : two) {
    for (auto y : x) cout << y << " ";
    cout << one[p][0] << '\n';
    p++;
  }
  for (p; p < one.size(); p += 3) {
    for (int j = p; j < p + 3; j++) cout << one[j][0] << " ";
    cout << '\n';
  }
  return 0;
}
