#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <climits>
#include <cmath>
#include <complex>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <vector>
#include <stack>
using namespace std;
#define int long long
#define mp make_pair
#define fi first
#define pii pair<int,int>
#define se second
const int INF=1000000000000000000;
//const int INF=1e9;
const int N=1000000;
const int M=998244353;
const int ln=20;
template<typename T>
std::ostream& operator<< (std::ostream& os,pair<T,T> p){
return os << p.fi << "," << p.se << " ";
}
void solve(){
int n,k;
cin >> n >> k;
int a[n];
for(int i=0;i<n;i++) cin >> a[i];
vector<pii> v;
for(int i=0;i<n;i++) v.push_back(mp(-a[i],i));
sort(v.begin(),v.end());
int sum=0;
for(int i=0;i<n;i++){
sum+=a[i];
}
if(sum%k!=0){
cout << -1 << '\n';
return;
}
sum/=k;
sum+=v[0].fi;
if(sum<0){
cout << -1 << "\n";
return;
}
vector<pair<int,vector<int>>> ans;
while(!v.empty()){
if(v.back().fi==0){
v.pop_back();
continue;
}
int m=v.size();
if(sum>0){
int op=min(sum,-v.back().fi);
ans.push_back(mp(op,vector<int>()));
for(int j=1;j<=k;j++){
int ind=v[m-j].se;
ans.back().se.push_back(ind);
v[m-j].fi+=op;
}
sum-=op;
continue;
}
if(m<k){
for(auto [j,i]:v){
cout << i << " " << -j << "ygtyfuftyu\n";
}
assert(false);
}
int op=-v.back().fi;
ans.push_back(mp(op,vector<int>()));
ans.back().se.push_back(v[0].se);
for(int j=1;j<=k-1;j++){
int ind=v[m-j].se;
ans.back().se.push_back(ind);
v[m-j].fi+=op;
}
v[0].fi+=op;
}
cout << ans.size() << "\n";
for(auto [x,v]:ans){
cout << x << " ";
for(int i:v) cout << i+1 << " ";
cout << "\n";
}
}
signed main(){
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int t;
//cin >> t;
t=1;
while(t--) solve();
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
}
