#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
//#include<bits/extc++.h>
//__gnu_pbds
#define int ll
signed main(){
ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
int n,k;cin>>n>>k;
ll sum=0;
vector<int> arr(n);
priority_queue<pair<int,int> > pq;
for(int i=0;i<n;i++){
cin>>arr[i];
sum+=arr[i];
pq.push({arr[i],i});
}
if(sum%k){
cout<<-1<<"\n";
return 0;
}
if(pq.top().first>sum/k){
cout<<-1<<"\n";
return 0;
}
vector<vector<int>> ans;
while(sum){
vector<int> v;
ll tomi = LONG_LONG_MAX;
for(int i=0;i<k;i++){
v.push_back(pq.top().second);
tomi = pq.top().first;
pq.pop();
}
if(pq.size()) tomi = min(tomi,(sum/k)-pq.top().first);
sum-=k*tomi;
vector<int> tempans;
tempans.push_back(tomi);
for(auto i : v){
tempans.push_back(i+1);
arr[i]-=tomi;
if(arr[i]) pq.push({arr[i],i});
}
ans.push_back(tempans);
}
cout<<ans.size()<<"\n";
for(auto ar : ans){
for(auto v : ar){
cout<<v<<" ";
}
cout<<"\n";
}
return 0;
}
