#include "bits/stdc++.h"
// @JASPER'S BOILERPLATE
using namespace std;
using ll = long long;
#ifdef JASPER
#include "debug.h"
#else
#define debug(...) 166
#endif
const int N = 1e6 + 5;
const ll INF = 1e18 + 5;
int n, k;
ll a[N];
signed main() {
cin.tie(0) -> sync_with_stdio(0);
cin >> n >> k;
for (int i = 1; i <= n; ++i) cin >> a[i];
ll sum = accumulate(a + 1, a + 1 + n, 0LL);
ll mx = *max_element(a + 1, a + 1 + n);
if (sum % k || mx > sum / k) {
cout << "-1\n";
return 0;
}
using T = pair <ll, ll>;
priority_queue <T> q;
for (int i = 1; i <= n; ++i)
q.push(make_pair(a[i], i));
vector <vector <ll>> ans;
// Take k max values
while ((int) q.size() >= k) {
int take = 0;
vector <T> opts;
while (!q.empty()) {
if (take == k) break;
opts.push_back(q.top());
q.pop();
++take;
}
ll y = (q.empty()? -1 : q.top().first);
// subtract value
ll x;
if (y == -1) x = opts.back().first;
else x = min(1LL * opts.back().first, (sum - y * k) / k);
vector <ll> ids;
ids.push_back(x);
for (auto [val, id] : opts) {
a[id] -= x;
ids.push_back(id);
if (a[id] > 0)
q.push(make_pair(a[id], id));
}
sum -= 1LL * k * x;
ans.push_back(ids);
}
cout << (int) ans.size() << "\n";
for (auto x : ans) {
for (ll j : x) cout << j << " ";
cout << "\n";
}
}
