#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <set>
#include <stack>
#include <map>
#include <queue>
#include <vector>
#include <cstring>
#include <array>
#include <bitset>
using namespace std;
typedef long long ll;
const int maxn=1e6+5;
ll a[maxn];
set < ll > s;
set < pair < ll, int > > s1;
vector < vector < ll > > q;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, k;
cin >> n >> k;
ll sum=0;
s.insert(0);
for(int i=0; i<n; i++){
cin >> a[i];
sum+=a[i];
s.insert(a[i]);
s1.insert({a[i], i});
}
if(sum%k){
cout << -1 << '\n';
return 0;
}
ll val;
set < pair < ll, int > >::iterator it;
vector < ll > v;
vector < pair < ll, int > > ins;
set < ll >::iterator it1;
while(!s1.empty()){
if((int)s1.size()==k){
it=s1.begin();
val=it->first;
v.push_back(val);
for(int i=0; i<k; i++){
v.push_back(it->second+1);
if(val!=it->first){
cout << -1 << '\n';
return 0;
}
it++;
}
s1.clear();
}
else{
it=--s1.end();
for(int i=0; i<k; i++){
it--;
}
val=it->first;
it1=s.lower_bound(val);
it1--;
val=*it1;
it++;
val=it->first-val;
v.push_back(val);
it=--s1.end();
for(int i=0; i<k; i++){
v.push_back(it->second+1);
it--;
}
it=--s1.end();
for(int i=0; i<k; i++){
ins.push_back({it->first-val, it->second});
it=s1.erase(it);
it--;
}
for(int i=0; i<k; i++){
if(ins[i].first){
s1.insert(ins[i]);
}
}
ins.clear();
}
q.push_back(v);
v.clear();
}
cout << q.size() << '\n';
for(int i=0; i<(int)q.size(); i++){
for(int j=0; j<(int)q[i].size(); j++){
cout << q[i][j] << ' ';
}
cout << '\n';
}
return 0;
}
