#include<bits/stdc++.h>
int main() {
   int n;
   scanf("%d", &n);
   std::vector<std::tuple<int> > s0, s2;
   std::vector<std::tuple<int, int> > s01, s21;
   std::vector<std::tuple<int, int, int> > s012, s210, s021;
   std::vector<std::tuple<int, int, int, int> > s0121, s2101;
   #define val(x, y) (std::get<(x)>((y)))
   for (int i = 0, x; i < n; i++) {
      scanf("%d", &x), x--;
      if (x == 0) {
         if (s21.size()) {
            auto _ = s21.back();
            s210.emplace_back(val(0, _), val(1, _), i);
            s21.pop_back();
         } else if (s021.size()) {
            auto _  = s021.back();
            s210.emplace_back(val(1, _), val(2, _), i);
            s0.emplace_back(val(0, _));
            s021.pop_back();
         } else if (s0121.size()) {
            auto _ = s0121.back();
            s210.emplace_back(val(2, _), val(3, _), i);
            s01.emplace_back(val(0, _), val(1, _));
            s0121.pop_back();
         } else if (s2101.size()) {
            auto _ = s2101.back();
            s210.emplace_back(val(0, _), val(1, _), i);
            s01.emplace_back(val(2, _), val(3, _));
            s2101.pop_back();
         } else
            s0.emplace_back(i);
      } else if (x == 1) {
         if (s0.size() && s2.size()) {
            auto _0 = s0.back(), _2 = s2.back();
            s021.emplace_back(val(0, _0), val(0, _2), i);
            s0.pop_back(), s2.pop_back();
         } else if (s0.size()) {
            auto _ = s0.back();
            s01.emplace_back(val(0, _), i);
            s0.pop_back();
         } else if (s2.size()) {
            auto _ = s2.back();
            s21.emplace_back(val(0, _), i);
            s2.pop_back();
         } else if (s021.size()) {
            auto _ = s021.back();
            s01.emplace_back(val(0, _), val(2, _));
            s21.emplace_back(val(1, _), i);
            s021.pop_back();
         } else if (s012.size()) {
            auto _ = s012.back();
            s0121.emplace_back(val(0, _), val(1, _), val(2, _), i);
            s012.pop_back();
         } else if (s210.size()) {
            auto _ = s210.back();
            s2101.emplace_back(val(0, _), val(1, _), val(2, _), i);
            s210.pop_back();
         }
      } else {
         if (s01.size()) {
            auto _ = s01.back();
            s012.emplace_back(val(0, _), val(1, _), i);
            s01.pop_back();
         } else if (s021.size()) {
            auto _  = s021.back();
            s012.emplace_back(val(0, _), val(2, _), i);
            s2.emplace_back(val(1, _));
            s021.pop_back();
         } else if (s2101.size()) {
            auto _ = s2101.back();
            s012.emplace_back(val(2, _), val(3, _), i);
            s21.emplace_back(val(0, _), val(1, _));
            s2101.pop_back();
         } else if (s0121.size()) {
            auto _ = s0121.back();
            s012.emplace_back(val(0, _), val(1, _), i);
            s21.emplace_back(val(2, _), val(3, _));
            s0121.pop_back();
         } else
            s2.emplace_back(i);
      }
   }
   printf("%zu\n", s012.size() + s210.size() + s0121.size() + s2101.size());
   for (auto _ : s012)
      printf("%d %d %d\n", val(0, _), val(1, _), val(2, _));
   for (auto _ : s210)
      printf("%d %d %d\n", val(0, _), val(1, _), val(2, _));
   for (auto _ : s0121)
      printf("%d %d %d\n", val(0, _), val(1, _), val(2, _));
   for (auto _ : s2101)
      printf("%d %d %d\n", val(0, _), val(1, _), val(2, _));
   return 0;
}