#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using i128 = __int128;
using u128 = unsigned __int128;
template <typename T>
void chkmax(T &x, const T &y) {
  if (x < y) x = y;
}
template <typename T>
void chkmin(T &x, const T &y) {
  if (y < x) x = y;
}
constexpr int MAXN = 15010;
int n, m, sum, a[MAXN], lim[MAXN];
bool can[MAXN];
vector<bitset<MAXN>> dp[MAXN];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> a[i];
    sum += a[i];
    ++lim[1];
    --lim[a[i] + 1];
  }
  for (int i = 1; i <= sum; ++i) lim[i] += lim[i - 1];
  for (int i = 1; i <= sum; ++i) lim[i] += lim[i - 1];
  cin >> m;
  for (int i = 1, x; i <= m; ++i) {
    cin >> x;
    can[x] = true;
  }
  if (lim[1] == sum && can[sum]) {
    cout << "1\n" << n << " ";
    for (int i = 1; i <= n; ++i) cout << i << " \n"[i == n];
    return 0;
  }
  dp[1].resize(lim[1] + 1);
  for (int i = 1; i <= lim[1]; ++i)
    if (can[i]) dp[1][i][i] = 1;
  bitset<MAXN> now;
  for (int i = 1; i <= lim[1]; ++i) now[i] = 1;
  for (int i = 2; i <= sum; ++i) {
    for (int j = lim[i - 1] + 1; j <= lim[i]; ++j) now[j] = 1;
    bitset<MAXN> tmp;
    dp[i].resize(lim[i] / i + 1);
    for (int j = lim[i] / i, k = lim[i - 1] / (i - 1); j >= 1; --j) {
      if (!can[j]) continue;
      while (k >= j) tmp |= dp[i - 1][k--];
      dp[i][j] = tmp << j & now;
      if (dp[i][j][sum]) {
        cout << i << "\n";
        vector<int> vec;
        for (; i; --i) {
          while (!dp[i][j][sum]) ++j;
          vec.emplace_back(j);
          sum -= j;
        }
        vector<vector<int>> wys(vec.size());
        priority_queue<pair<int, int>> pq;
        for (int l = 0; l < (int)vec.size(); ++l) pq.emplace(vec[l], l);
        for (int l = 1; l <= n; ++l) {
          vector<pair<int, int>> temp;
          while (a[l]--) {
            int u = pq.top().second;
            temp.emplace_back(pq.top().first - 1, u);
            pq.pop();
            wys[u].emplace_back(l);
          }
          for (auto &s : temp) pq.emplace(s);
        }
        for (auto &l : wys) {
          cout << l.size() << " ";
          for (auto s : l) cout << s << " ";
          cout << "\n";
        }
        return 0;
      }
    }
  }
  cout << "-1\n";
  return 0;
}
// g++ cookies.cpp -o cookies -Wall -Wextra -Wshadow -O2 -std=c++14 -fsanitize=address,undefined
/*
2
1 1
1
1
*/