#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int n,k; cin >> n >> k;
vector<pair<long long, int>> a(n);
long long s = 0;
for (int i = 0; i < n; i++) {
cin >> a[i].first;
a[i].second = i+1;
s += a[i].first;
}
sort(a.begin(),a.end(),greater<pair<long long, int>>());
if (s % k != 0 || s/k < a[0].first) {
cout << -1;
return 0;
}
s /= k;
long long d = 0, e = 0, x;
vector<long long> t(n), l(n);
int i = n-1, j = 0;
queue<pair<pair<int,int>, long long>> q;
while (i >= k) {
d -= t[i]; t[i] = 0;
e += l[j]; l[j] = 0;
x = min(a[i].first - d, s - (a[j].first-e));
if (x) q.push({{j,i},x});
t[i-k+j] += x;
l[i-k+j+1] += x;
s -= x;
if (x == a[i].first - d) i--;
else j++;
d += x;
}
q.push({{0,k-1},s});
cout << q.size() << '\n';
while (!q.empty()) {
cout << q.front().second << ' ';
for (i = 0; i < q.front().first.first; i++) cout << a[i].second << ' ';
for (i = q.front().first.second; i > q.front().first.second - k + q.front().first.first; i--) cout << a[i].second << ' ';
cout << '\n';
q.pop();
}
return 0;
}
