#include <bits/stdc++.h>
#define int long long
//#pragma GCC optimize("Ofast")
//#pragma comment(linker, "/stack:200000000")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4")
#define file(s) freopen(s".in","r",stdin); freopen(s".out","w",stdout);
#define fastio ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define all(x) x.begin(), x.end()
#define sz(s) (int)s.size()
#define pb push_back
#define ppb pop_back
#define mp make_pair
#define s second
#define f first
using namespace std;
typedef pair < long long, long long > pll;
typedef pair < int, int > pii;
typedef unsigned long long ull;
typedef vector < pii > vpii;
typedef vector < int > vi;
typedef long double ldb;
typedef long long ll;
typedef double db;
const int dx[] = {1, -1, 0, 0}, dy[] = {0, 0, 1, -1}, block = 555;
const pii base = mp(1171, 3307), Mod = mp(1e9 + 7, 1e9 + 9);
const int inf = 1e9, maxn = 4e5 + 148, mod = 1e9 + 7, N = 1e6 + 11;
const db eps = 1e-12, pi = 3.14159265359;
const ll INF = 1e18;
vector < pair < int, vi > > ans;
int n, m, k, a[N], sum;
set < int > pos, q;
vpii add, del;
vi Pos;
void f (int l, int r, int x) {
// cerr << l << ' ' << r << ' ' << x << endl;
pos.insert(l);
pos.insert(r + 1);
add.pb({l, x});
del.pb({r + 1, x});
}
main () {
fastio
scanf("%lld%lld", &n, &k);
for (int i = 1; i <= n; ++i) {
scanf("%lld", &a[i]);
sum += a[i];
}
m = sum / k;
if ((sum % k) || m < *max_element(a + 1, a + 1 + n)) {
cout << -1;
return 0;
}
int cur = 1;
for (int i = 1; i <= n; ++i) {
if (cur + a[i] - 1 > m) {
f(cur, m, i);
f(1, cur + a[i] - 1 - m, i);
} else
f(cur, cur + a[i] - 1, i);
cur += a[i];
if (cur > m)
cur -= m;
}
sort(all(add));
sort(all(del));
int j1 = 0, j2 = 0;
for (auto i : pos)
Pos.pb(i);
for (int j = 0; j < sz(Pos); ++j) {
int i = Pos[j];
while (j2 < sz(del) && del[j2].f == i) {
q.erase(del[j2].s);
++j2;
}
while (j1 < sz(add) && add[j1].f == i) {
q.insert(add[j1].s);
++j1;
}
if (j < sz(Pos) - 1) {
vi tmp;
for (auto x : q)
tmp.pb(x);
ans.pb({Pos[j + 1] - Pos[j], tmp});
// cerr << Pos[j + 1] << ' ' << Pos[j] << endl;
}
}
printf("%lld\n", sz(ans));
for (auto v : ans) {
printf("%lld ", v.f);
for (auto x : v.s)
printf("%lld ", x);
printf("\n");
}
}
