#include <bits/stdc++.h>
#define int long long
using namespace std;
#define file ""
#define mp make_pair
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define getbit(x, i) (((x) >> (i)) & 1)
#define bit(x) (1LL << (x))
#define popcount __builtin_popcountll
mt19937_64 rd(chrono::steady_clock::now().time_since_epoch().count());
int rand(int l, int r) {
return l + rd() % (r - l + 1);
}
const int N = 1e6 + 5;
const int mod = (int)1e9 + 7; // 998244353;
const int lg = 25; // lg + 1
const int oo = 1e9;
const long long ooo = 1e18;
template<class X, class Y> bool mini(X &a, Y b) {
return a > b ? (a = b, true) : false;
}
template<class X, class Y> bool maxi(X &a, Y b) {
return a < b ? (a = b, true) : false;
}
void add(int &a, int b) {
a += b;
if (a >= mod) a -= mod;
if (a < 0) a += mod;
}
int n, k;
int a[N];
int s;
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
// freopen(file".inp", "r", stdin);
// freopen(file".out", "w", stdout);
cin >> n >> k;
priority_queue<pair<int, int> > q;
for (int i = 1; i <= n; ++i) {
cin >> a[i];
s += a[i];
q.emplace(a[i], i);
}
if (s % k != 0) {
cout << -1;
return 0;
}
if (q.top().fi > s / k) {
cout << -1;
return 0;
}
vector<vector<int> > res;
while (s > 0) {
vector<int> id;
int rem = oo;
for (int i = 1; i <= k; ++i) {
id.push_back(q.top().se);
rem = q.top().fi;
q.pop();
}
if (q.size()) rem = min(rem, (s / k) - q.top().fi);
s -= k * rem;
vector<int> cur;
cur.push_back(rem);
for (int i : id) {
cur.push_back(i);
a[i] -= rem;
if (a[i] > 0) q.emplace(a[i], i);
}
res.push_back(cur);
}
cout << (int) res.size() << '\n';
for (auto cur : res) {
for (int i : cur) cout << i << ' ';
cout << '\n';
}
return 0;
}
/*
*/
