#include <bits/stdc++.h>
//#include<ext/pb_ds/assoc_container.hpp>
//#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
//using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
#define ii pair<int,int>
#define pll pair<ll,ll>
#define vi vector<int>
#define vii vector<ii>
#define vll vector<ll>
#define vpll vector<pll>
#define msi multiset<int>
#define si set<int>
#define PB push_back
#define PF push_front
#define PPB pop_back
#define PPF pop_front
#define X first
#define Y second
#define MP make_pair
#define FOR(i, a, b) for (int i = int(a); i < int(b); i++)
#define REP(i, n) FOR(i, 0, n)
#define all(x) (x).begin(), (x).end()
const int mod = 1e9 + 7;
const int MOD = 998244353;
const int inf = 1e8 + 7;
const ll INF = 1e18 + 7;
const int logo = 30;
const int MAXN = 1e6 + 2;
const int off = 1 << logo;
const int trsz = off << 1;
const int dx[] = {1, -1, 0, 0};
const int dy[] = {0, 0, -1, 1};
set<pll> act;
vector<vll> ans;
vll tr;
ll arr[MAXN];
void solve(){
int n;
ll k;
cin >> n >> k;
ll s = 0;
for(int i=1; i<=n; i++){
cin >> arr[i];
act.insert({arr[i], i});
s += arr[i];
}
if(s % k or (*act.rbegin()).X > (ll)(s / k)){
cout << -1 << "\n";
return;
}
while(!act.empty()){
ll tak = 0;
tr.clear();
for(int i=0; i<k; i++){
pll cr = *act.rbegin();
act.erase(--act.end());
tr.PB(cr.Y);
tak = cr.X;
}
if(act.size()) tak = min(tak, (ll)(s / k) - (ll)(*act.rbegin()).X);
for(auto &i : tr){
arr[i] -= (ll)tak;
s -= (ll)tak;
if(arr[i]) act.insert({(ll)arr[i], (ll)i});
}
reverse(all(tr));
tr.PB(tak);
reverse(all(tr));
ans.PB(tr);
}
cout << ans.size() << "\n";
for(auto &x : ans){
for(auto &y : x) cout << y << " ";
cout << "\n";
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
solve();
return 0;
}
