#include <bits/stdc++.h>
using namespace std;
int main() {
cin.tie(nullptr)->sync_with_stdio(false);
int n, m;
cin >> n;
vector<int> a(n);
for (int &i : a) { cin >> i; }
cin >> m;
vector<int> b(m);
for (int &i : b) { cin >> i; }
// m == 1
int tot_cookies = accumulate(a.begin(), a.end(), 0);
m = b[0];
if (tot_cookies % m != 0) {
cout << "-1\n";
return 0;
}
vector<vector<int>> ans;
for (int i = 0; i < tot_cookies / m; ++i) {
vector<int> box;
vector<int> ord(n);
iota(ord.begin(), ord.end(), 0);
sort(ord.begin(), ord.end(), [&](int i, int j) { return a[i] > a[j]; });
for (int &type : ord) {
if (a[type] == 0 || box.size() == m) { break; }
box.push_back(type);
a[type]--;
}
if (box.size() != m) {
cout << "-1\n";
return 0;
}
ans.push_back(box);
}
cout << ans.size() << '\n';
for (auto &box : ans) {
cout << box.size() << ' ';
for (int &i : box) { cout << i + 1 << ' '; }
cout << '\n';
}
}
