#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair <int, int>
#define fi first
#define se second
#define mp make_pair
#define isz(a) (int)(a).size()
const int NM = 1e5;
int N, K, a[NM+5];
priority_queue <pii> Q;
vector <pair <int, vector <int> > > ans;
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> N >> K;
int sum = 0, mx = 0;
for (int i = 1; i <= N; i++){
cin >> a[i];
sum += a[i];
mx = max(mx, a[i]);
Q.push(mp(a[i], i));
}
if (sum%K != 0 || mx > sum/K){
cout << -1;
return 0;
}
while (!Q.empty()){
pair <int, vector <int> > P = mp(0, vector <int>(0));
for (int i = 1; i <= K; i++){
P.se.push_back(Q.top().se);
Q.pop();
}
P.fi = a[P.se[K-1]];
if (!Q.empty()){
P.fi = min(P.fi, sum/K-Q.top().fi);
}
for (int i = 0; i < K; i++){
a[P.se[i]] -= P.fi;
if (a[P.se[i]] > 0) Q.push(mp(a[P.se[i]], P.se[i]));
}
sum -= P.fi*K;
ans.push_back(P);
}
cout << isz(ans) << '\n';
for (int i = 0; i < isz(ans); i++){
cout << ans[i].fi << ' ';
for (int x : ans[i].se) cout << x << ' ';
cout << '\n';
}
return 0;
}
