#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <climits>
#include <string>
#include <set>
#include <cmath>
#include <map>
#include <unordered_map>
#include <numeric>
#include <random>
#include <memory>
#include <chrono>
#include <functional>
#include <unordered_set>
#include <cstring>
#include <cassert>
#include <bitset>
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x...)
#endif
//#define int ll
//#pragma GCC optimize("Ofast")


using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair <int, int> pii;
#define sz(x) int((x).size())

#ifndef LOCAL
	mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#else
	mt19937 rng(228);
#endif

const int N = 3e5 + 7;
const int inf = INT_MAX / 2;
const ll INF = LLONG_MAX / 3;
const int MOD = 998244353;
const ld eps = 1e-6;
const string cars[] = {"🚗", "🚕", "🚙"};

int l[N], r[N], a[N];

struct Tree {
	int t[4 * N];

	Tree () {
		memset(t, -1, sizeof t);
	}

	void push(int v) {
		if (t[v] != -1) {
			t[2 * v] = t[2 * v + 1] = t[v];
			t[v] = -1;
		}
	}

	void update(int v, int tl, int tr, int l, int r, int val) {
		if (l > r) {
			return;
		}

		if (tl == l && tr == r) {
			t[v] = val;
		}
		else {
			push(v);

			int tm = (tl + tr) / 2;

			update(2 * v, tl, tm, l, min(r, tm), val);
			update(2 * v + 1, tm + 1, tr, max(l, tm + 1), r, val);
		}
	}

	int get(int v, int tl, int tr, int pos) {
		if (tl == tr) {
			return t[v];
		}
		else {
			push(v);

			int tm = (tl + tr) / 2;
			if (pos <= tm) {
				return get(2 * v, tl, tm, pos);
			}
			else {
				return get(2 * v + 1, tm + 1, tr, pos);
			}
		}
	}
};

signed main() {
#ifdef LOCAL
	freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
#endif
	cout << fixed << setprecision(9);
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);

	Tree tree = Tree();

	int n, m;
	cin >> n >> m;

	fill(l, l + N, inf);
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		l[a[i]] = min(i, l[a[i]]);
		r[a[i]] = max(i, r[a[i]]);
	}

	vector < tuple < int, int, int > > v;
	for (int i = 1; i <= m; i++) {
		if (l[i] != inf) {
			v.emplace_back(l[i], r[i], i);
		}
	}

	sort(v.begin(), v.end());

	set < int > s;
	for (auto x : v) {
		int l, r, c;
		tie(l, r, c) = x;
		debug(l, r, c);

		if (!s.empty() && l <= *s.rbegin() && r > *s.rbegin()) {
			return cout << "-1\n", 0;
		}

		s.insert(r);
	}

	sort(v.begin(), v.end(), [](tuple < int, int, int > x, tuple < int, int, int > y) {
		return get < 0 > (x) < get < 0 > (y);
 	});

 	
 	for (auto x : v) {
 		int l, r, c;
 		tie(l, r, c) = x;

 		//cout << c << " " << l + 1 << " " << r + 1 << "\n";
 		tree.update(1, 0, n - 1, l, r, c);
 	}

 	int flag = 1;
 	for (int i = 0; i < n; i++) {
 		if (tree.get(1, 0, n - 1, i) != a[i]) {
 			flag = 0;
 			break;
 		}
 	}

 	if (flag) {
 		cout << sz(v) << "\n";
 		for (auto x : v) {
	 		int l, r, c;
	 		tie(l, r, c) = x;

	 		cout << c << " " << l + 1 << " " << r + 1 << "\n";
	 		//tree.update(1, 0, n - 1, l, r, c);
	 	}
 	}
 	else {
 		cout << "-1\n";
 	}

	return 0;
}