#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 1000010;
int n, k;
ll a[MAX_N];
void fail() { puts("-1"), exit(0); }
int32_t main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> n >> k;
for (int i = 0;i < n;++i)
cin >> a[i];
ll sum = accumulate(a, a+n, 0ll), y = sum / k;
if (sum % k) fail();
if (*max_element(a, a+n) > y) fail();
map<ll, vector<int>> sweep;
// [l, r)
auto addin = [&](int index, ll l, ll r) {
sweep[l].pb(index), sweep[r].pb(index);
};
DE(y);
{
ll v = 0;
for (int i = 0;i < n;++i) {
ll l = v, r = l + a[i];
DE(i, l, r);
if (r >= y) {
addin(i, l, y);
addin(i, 0, r-=y);
}
else {
addin(i, l, r);
}
v = r;
}
}
vector< pair<ll, vector<int>> > res;
{
ll lstc = 0;
set<int> cur;
for (auto [c, vec] : sweep) {
ll wid = c - lstc; lstc = c;
if (wid) {
res.pb(wid, vector<int>(AI(cur)));
assert(cur.size() == k);
}
DE(c), debug(AI(cur));
for (int ind : vec) {
if (cur.count(ind)) cur.erase(ind);
else cur.insert(ind);
}
if (c == y) {
assert(cur.empty());
break;
}
}
}
cout << res.size() << '\n';
for (auto [X, vec] : res) {
cout << X;
for (int ind : vec) cout << ' ' << ind+1;
cout << '\n';
}
}
