#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 pli pair<ll, int>
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
int n, k;
cin >> n >> k;
vector<ll> a(n);
for (auto &i : a)
cin >> i;
ll sm = accumulate(all(a), 0LL);
if (sm % k || *max_element(all(a)) > sm / k) return cout << -1, 0;
vector<ll> u = {0};
vector<deque<pli>> v = {{}};
for (int i = 0; i < n; i++) {
if (a[i] <= sm / k - u.back()) {
u.back() += a[i];
v.back().push_back({a[i], i});
}
else {
if (sm / k != u.back()) v.back().push_back({sm / k - u.back(), i});
v.push_back({{a[i] - sm / k + u.back(), i}});
u.push_back(a[i] - sm / k + u.back());
}
}
vector<vector<ll>> ans;
while (!v[0].empty()) {
ll mn = LLONG_MAX;
for (int i = 0; i < k; i++)
mn = min(mn, v[i].front().ff);
ans.push_back({mn});
for (int i = 0; i < k; i++) {
ans.back().push_back(v[i].front().ss + 1);
v[i].front().ff -= mn;
if (!v[i].front().ff) v[i].pop_front();
}
}
cout << sz(ans) << '\n';
for (auto i : ans) {
for (auto j : i)
cout << j << ' ';
cout << '\n';
}
}
