#include <bits/stdc++.h>
using namespace std;
void dfs(long long node, vector<vector<long long>>& adj, vector<long long>& vis,
         vector<long long>& cc) {
  vis[node] = 1;
  cc.push_back(node);
  for (auto x : adj[node]) {
    if (vis[x] == 0) {
      dfs(x, adj, vis, cc);
    }
  }
  return;
}
int32_t main() {
  long long t = 1;
  while (t--) {
    long long n, m;
    cin >> n >> m;
    vector<vector<long long>> adj(n + 1);
    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);
    }
    long long sz = n / 3;
    long long flag = 0;
    vector<vector<long long>> ans;
    vector<long long> vis(n + 1, 0);
    vector<vector<long long>> fgf;
    for (long long i = 1; i <= n; i++) {
      if (vis[i] == 0) {
        vector<long long> cc;
        dfs(i, adj, vis, cc);
        if (cc.size() > 3) {
          flag = 1;
        } else {
          fgf.push_back(cc);
        }
      }
    }
    if (flag) {
      cout << "-1" << '\n';
    } else {
      vector<long long> single;
      for (auto x : fgf) {
        if (x.size() == 1) {
          single.push_back(x[0]);
        }
      }
      long long i = 0;
      for (long long g = 0; g < fgf.size(); g++) {
        if (fgf[g].size() == 2) {
          if (i < single.size()) {
            fgf[g].push_back(single[i]);
            i++;
          }
        }
      }
      for (auto x : fgf) {
        if (x.size() == 3) {
          ans.push_back(x);
        } else if (x.size() == 2) {
          flag = 1;
        }
      }
      if (flag) {
        cout << "-1" << '\n';
      } else {
        if (single.size() >= 3) {
          for (long long j = i; j <= single.size() - 3; j += 3) {
            ans.push_back({single[j], single[j + 1], single[j + 2]});
          }
        }
        for (auto x : ans) {
          for (auto z : x) {
            cout << z << " ";
          }
          cout << '\n';
        }
      }
    }
  }
  return 0;
}
