#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pl = pair<ll,ll>;
using pii = pair<int,int>;
using tpl = tuple<int,int,int>;
#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int n, k; cin >> n >> k;
vector<ll> a(n);
for (ll &u : a) cin >> u;
ll sum = accumulate(all(a), 0LL);
if (sum % k) return cout << -1 << "\n", 0;
priority_queue<pii> pq;
for (int i = 0; i < n; i++) pq.emplace(a[i], i);
vector<pair<int,vector<int>>> opr;
for (int i = 0; i < sum / k; i++) {
vector<int> pos; vector<pii> wait;
for (int j = 0; j < k; j++) {
if (pq.empty()) return cout << -1 << "\n", 0;
int a, idx; tie(a, idx) = pq.top(); pq.pop();
pos.push_back(idx + 1);
if (a > 1) wait.emplace_back(a - 1, idx);
}
for (auto [a, b] : wait) pq.emplace(a, b);
opr.emplace_back(1, pos);
}
cout << opr.size() << "\n";
for (auto [a, vec] : opr) {
cout << a << " ";
for (int u : vec) cout << u << " ";
cout << "\n";
}
return 0;
}
