#include <bits/stdc++.h>

using namespace std;

const int N = 6e5;

int n;
vector<int> s0, s2;
vector<pair<int, int>> s01, s21;
vector<tuple<int, int, int>> s012, s021;
vector<tuple<int, int, int, int>> s0121;
tuple<int, int, int> operator+(pair<int, int> a, int b) { return {a.first, a.second, b}; }
tuple<int, int, int, int> operator+(tuple<int, int, int> a, int b) { return {get<0>(a), get<1>(a), get<2>(a), b}; }

int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; ++i) {
    int x; scanf("%d", &x), --x;
    if (x == 2) {
      if (!s01.empty()) s012.emplace_back(s01.back().first, s01.back().second, i), s01.pop_back();
      else if (!s021.empty()) s012.emplace_back(get<0>(s021.back()), get<2>(s021.back()), i), s2.push_back(get<1>(s021.back())), s021.pop_back();
      else if (!s0121.empty()) s012.emplace_back(get<0>(s0121.back()), get<1>(s0121.back()), i), s21.emplace_back(get<2>(s0121.back()), get<3>(s0121.back())), s0121.pop_back();
      else s2.push_back(i);
    } else if (x == 0) {
      if (!s21.empty()) s012.emplace_back(i, s21.back().second, s21.back().first), s21.pop_back();
      else if (!s021.empty()) s012.emplace_back(i, get<2>(s021.back()), get<1>(s021.back())), s0.push_back(get<0>(s021.back())), s021.pop_back();
      else if (!s0121.empty()) s012.emplace_back(i, get<3>(s0121.back()), get<2>(s0121.back())), s01.emplace_back(get<0>(s0121.back()), get<1>(s0121.back())), s0121.pop_back();
      else s0.push_back(i);
    } else {
      if (!s0.empty() && !s2.empty()) s021.emplace_back(s0.back(), s2.back(), i), s0.pop_back(), s2.pop_back();
      else if (!s0.empty()) s01.emplace_back(s0.back(), i), s0.pop_back();
      else if (!s2.empty()) s21.emplace_back(s2.back(), i), s2.pop_back();
      else if (!s021.empty()) s01.emplace_back(get<0>(s021.back()), get<2>(s021.back())), s21.emplace_back(get<1>(s021.back()), i), s021.pop_back();
      else if (!s012.empty()) {
        if (get<0>(s012.back()) < get<2>(s012.back()))
          s0121.emplace_back(get<0>(s012.back()), get<1>(s012.back()), get<2>(s012.back()), i);
        else
          s0121.emplace_back(get<0>(s012.back()), i, get<2>(s012.back()), get<1>(s012.back()));
        s012.pop_back();
      }
    }
  }
  printf("%d\n", (int)(s012.size() + s0121.size()));
  for (auto [i, j, k] : s012) printf("%d %d %d\n", min(i, k), j, max(i, k));
  for (auto [i, j, k, l] : s0121)
    if (i < k) printf("%d %d %d\n", i, j, k);
    else printf("%d %d %d\n", k, l, i);
}