#include <bits/stdc++.h>
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
using namespace std;
#define int long long int
const int N = 3e5 + 10;
const int md = 1e9 + 7;
const int INF = 1e18;
int32_t main(int32_t argc, char *argv[]) {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int T = 1;
// cin >> T;
while (T--) {
int n, k;
cin >> n >> k;
vector<int> a(n);
map<int, int> mp;
for (int i = 0; i < n; i++) {
cin >> a[i];
mp[a[i]]++;
}
if (k == 2 && (int) mp.size() != 1) {
multiset<pair<int, int>> s;
for (int i = 0; i < n; i++)
s.insert({a[i], i + 1});
bool ok = 0;
vector<pair<int, pair<int, int>>> ans;
while (true) {
auto it = s.end(), it1 = s.end();
it--, it--, it1--;
if (!((*it).first) xor !((*it1).first))
break;
if (!((*it).first) && !((*it1).first)) {
ok = 1;
break;
}
auto pr = *it, pr1 = *it1;
ans.push_back({1ll, {pr.second, pr1.second}});
s.erase(it), s.erase(it1);
s.insert({pr.first - 1ll, pr.second});
s.insert({pr1.first - 1ll, pr1.second});
}
if (ok) {
cout << (int) ans.size() << '\n';
for (auto i : ans)
cout << i.first << " " << i.second.first << " " << i.second.second << '\n';
} else {
cout << -1 << '\n';
}
} else if (mp.size() == 1) {
if (n % k)
cout << -1 << '\n';
else {
cout << (n / k) << '\n';
for (int i = 0; i < n; i += k) {
cout << a[i] << " ";
for (int j = i; j < i + k; j++)
cout << j + 1 << " ";
cout << '\n';
}
}
}
}
return 0;
}
