#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;
}