#include "bits/stdc++.h"
using namespace std;
#define int long long
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define endl '\n'
/*
implement and debug smart
DONT GET STUCK ON ONE APPROACH
write smth on paper
edge cases (n=1?)
rewrite the problem
simplify
transform the problem into other problem
*/
void solve(){
int n,k;
cin >> n >> k;
int ar[n+5];
int sum=0;
for(int i=1;i<=n;i++){
cin >> ar[i];
sum+=ar[i];
}
if(sum%k){
cout << -1 << endl;
return;
}
deque<int> cur;
vector<deque<int>> ans;
vector<array<int,2>> v;
for(int i=1;i<=n;i++){
v.pb({ar[i],i});
}
sort(all(v));
for(int i=0;i<k;i++) cur.pb(v[i][1]);
for(int i=0;i<n;i++){
if(v[i][0]==0){
cur.pop_front();
continue;
}
if(sz(cur)<k){
for(int j=min(i+sz(cur),n);j<min(n,i+k);j++) cur.pb(v[j][1]);
if(sz(cur)<k){
cout << -1 << endl;
return;
}
}
for(int j=0;j<v[i][0];j++) ans.pb(cur);
int u = v[i][0];
for(int j=i;j<i+k;j++) v[j][0]-=u;
cur.pop_front();
}
cout << sz(ans) << endl;
for(deque<int> x:ans){
cout << 1 << " ";
for(int u : x) cout << u << " ";
cout << endl;
}
}
int32_t main(){
cin.tie(0);
ios::sync_with_stdio(0);
int t=1;//cin >> t;
while(t--) solve();
}
