na eto bol'no smotret'

#include <bits/stdc++.h>

#define endl "\n"
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;

constexpr int N = 2e3 + 5;


ll m, n, l = 0, r = n, mid;
vector<pair<ll, int>> a, b;
vector<tuple<int, int, int>> ans;


void Solve()
{
  cin >> m >> n;
  for (int i = 0, v; i < m; i++)
    cin >> v, a.emplace_back(v, i);
 for (int i = 0, v; i < n; i++)
    cin >> v, b.emplace_back(v, i);
  sort(a.begin(), a.end());
  sort(b.begin(), b.end());
  for (int s = (b.size() - 1) / 2, f = b.size() - 1, cur = a.size() - 1; cur >= 0 && s >= 0 &&  f > (b.size() - 1) / 2; f--, cur--, s--)
  {
    while(a[cur].first >= b[f].first)
      cur--;
    while (s >= 0 && b[s].first >= a[cur].first)
      s--;
    if (s >= 0 && b[s].first < a[cur].first && a[cur].first < b[f].first)
      ans.emplace_back(a[cur].second, b[s].second, b[f].second);
  }
  cout << ans.size() << endl;
  for (auto [a, b, c]: ans)
    cout << a + 1 << " " << b + 1 << " " << c + 1 << endl;
}

int main()
{
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  Solve();
  return 0;
}