#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
template <typename T>
void ckmn(T& a, T b) {
  a = min(a, b);
}
template <typename T>
void ckmx(T& a, T b) {
  a = max(a, b);
}
void rd(int& x) { scanf("%i", &x); }
void rd(long long& x) { scanf("%lld", &x); }
void rd(char* x) { scanf("%s", x); }
void rd(double& x) { scanf("%lf", &x); }
void rd(string& x) { scanf("%s", &x); }
template <typename T1, typename T2>
void rd(pair<T1, T2>& x) {
  rd(x.first);
  rd(x.second);
}
template <typename T>
void rd(vector<T>& x) {
  for (T& i : x) rd(i);
}
template <typename T, typename... A>
void rd(T& x, A&... args) {
  rd(x);
  rd(args...);
}
template <typename T>
void rd() {
  T x;
  rd(x);
  return x;
}
int ri() {
  int x;
  rd(x);
  return x;
}
template <typename T>
vector<T> rv(int n) {
  vector<T> x(n);
  rd(x);
  return x;
}
template <typename T>
void ra(T a[], int n, int st = 1) {
  for (int i = 0; i < n; ++i) rd(a[st + i]);
}
template <typename T1, typename T2>
void ra(T1 a[], T2 b[], int n, int st = 1) {
  for (int i = 0; i < n; ++i) rd(a[st + i]), rd(b[st + i]);
}
template <typename T1, typename T2, typename T3>
void ra(T1 a[], T2 b[], T3 c[], int n, int st = 1) {
  for (int i = 0; i < n; ++i) rd(a[st + i]), rd(b[st + i]), rd(c[st + i]);
}
void re(vector<int> E[], int m, bool dir = 0) {
  for (int i = 0, u, v; i < m; ++i) {
    rd(u, v);
    E[u].push_back(v);
    if (!dir) E[v].push_back(u);
  }
}
template <typename T>
void re(vector<pair<int, T>> E[], int m, bool dir = 0) {
  for (int i = 0, u, v; i < m; ++i) {
    T w;
    rd(u, v, w);
    E[u].push_back({v, w});
    if (!dir) E[v].push_back({u, w});
  }
}
const int N = 1205;
int type[N], tot;
vector<int> my[N], E[N];
vector<vector<int>> ans;
struct cmp {
  bool operator()(int i, int j) {
    return make_pair(E[i].size(), i) > make_pair(E[j].size(), j);
  }
};
int main() {
  int n = ri();
  for (int i = 1; i <= 3 * n; i++) type[ri()] = 1;
  stack<int> stk, leaf;
  for (int i = 1; i <= 6 * n; i++) {
    if (stk.empty() || type[my[stk.top()][0]] != type[i]) {
      tot++;
      my[tot].push_back(i);
      stk.push(tot);
    } else {
      my[stk.top()].push_back(i);
      if (my[stk.top()].size() == 3) {
        int u = stk.top();
        stk.pop();
        while (leaf.size() && my[leaf.top()][0] > my[u][0]) {
          E[u].push_back(leaf.top());
          leaf.pop();
        }
        leaf.push(u);
      }
    }
  }
  assert(stk.empty());
  set<int, cmp> st[2];
  while (leaf.size()) {
    st[type[my[leaf.top()][0]]].insert(leaf.top());
    leaf.pop();
  }
  for (int i = 1; i <= n; i++) {
    int j = *st[0].begin();
    st[0].erase(j);
    ans.push_back(my[j]);
    for (int k : E[j]) st[1].insert(k), assert(type[my[k][0]] == 1);
    j = *st[1].begin();
    st[1].erase(j);
    ans.push_back(my[j]);
    for (int k : E[j]) st[0].insert(k), assert(type[my[k][0]] == 0);
  }
  reverse(ans.begin(), ans.end());
  for (auto v : ans) {
    for (int i : v) printf("%i ", i);
    printf("\n");
  }
  return 0;
}
