#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define sz(v) (int)(v).size()
#define all(v) (v).begin(), (v).end()
#define ff first
#define ss second
#define pii pair<int, int>
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
int n, k;
cin >> n >> k;
ll sm = 0;
set<pii> s;
for (int i = 0; i < n; i++) {
int x;
cin >> x;
sm += x;
s.insert({x, i});
}
if (sm % k) return cout << -1, 0;
vector<vector<int>> ans;
while ((*--s.end()).ff) {
if (sz(s) < k) return cout << -1, 0;
vector<pii> v;
ans.push_back({});
for (int i = 0; i < k; i++) {
auto t = --s.end();
ans.back().push_back((*t).ss);
if ((*t).ff) v.push_back({(*t).ff - 1, (*t).ss});
s.erase(t);
}
for (auto i : v)
s.insert(i);
}
cout << sz(ans) << '\n';
for (auto i : ans) {
cout << "1 ";
for (auto j : i)
cout << j + 1 << ' ';
cout << '\n';
}
}
