This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  int m;
  cin >> m;
  vector<int> b(m);
  for (int i = 0; i < m; i++) {
    cin >> b[i];
  }
  reverse(b.begin(), b.end());
  int s = accumulate(a.begin(), a.end(), 0);
  vector<long long> limit(s + 1);
  for (int i = 0; i < n; i++) {
    for (int j = 1; j <= s; j++) {
      limit[j] += min(j, a[i]);
    }
  }
  const int inf = (int) 1e9;
  const int MAX = 15015;
  vector<vector<bitset<MAX>>> dp(m);
  for (int i = 0; i < m; i++) {
    int t = (s / b[i]) + 1;
    dp[i] = vector<bitset<MAX>>(t);
  }
  dp[0][0][0] = 1;
  for (int i = 0; i < m; i++) {
    if (i > 0) {
      for (int j = 0; j < (int) dp[i - 1].size(); j++) {
        dp[i][j] = dp[i - 1][j];
      }
    }
    for (int j = 0; j + 1 < (int) dp[i].size(); j++) {
      for (int k = 0; k + b[i] <= s; k++) {
        if (dp[i][j][k] == 1 && limit[j + 1] >= k + b[i]) {
          dp[i][j + 1][k + b[i]] = 1;
        }
      }
      // dp[i][j + 1] = (dp[i][j + 1] | ((dp[i][j] << (MAX - limit[j + 1])) >> (MAX - limit[j + 1])));
    }
  }
  int p = 0;
  for (int i = 0; i < (int) dp[m - 1].size(); i++) {
    if (dp[m - 1][i][s]) {
      p = i;
      break;
    }
  }
  if (!dp[m - 1][p][s]) {
    cout << -1 << '\n';
    return 0;
  }
  vector<int> v;
  int i = m - 1, j = p, k = s;
  while (i != -1) {
    if ((i == 0 && j == 0) || (i > 0 && j < (int) dp[i - 1].size() && dp[i - 1][j][k] == 1)) {
      i -= 1;
      continue;
    }
    v.push_back(b[i]);
    j -= 1;
    k -= b[i];
  }
  sort(v.rbegin(), v.rend());
  int sz = (int) v.size();
  vector<vector<int>> ids(sz);
  set<pair<int, int>> st;
  for (int i = 0; i < n; i++) {
    st.emplace(a[i], i);
  }
  for (int i = 0; i < sz; i++) {
    vector<int> p;
    for (int foo = 0; foo < v[i]; foo++) {
      auto it = prev(st.end());
      int id = it->second;
      st.erase(it);
      ids[i].emplace_back(id);
      a[id] -= 1;
      if (a[id] > 0) {
        p.push_back(id);
      }
    }
    for (int j : p) {
      st.emplace(a[j], j);
    }
  }
  cout << sz << '\n';
  for (int i = 0; i < sz; i++) {
    cout << (int) ids[i].size() << " ";
    for (int j : ids[i]) {
      cout << j + 1 << " ";
    }
    cout << '\n';
  }
  return 0;
}
Compilation message (stderr)
cookies.cpp: In function 'int main()':
cookies.cpp:28:13: warning: unused variable 'inf' [-Wunused-variable]
   28 |   const int inf = (int) 1e9;
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