#include <bits/stdc++.h>
#pragma GCC optimize("-O2")
using namespace std;
void err(istream_iterator<string> it) { cerr << endl; }
template <typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << "\t";
  err(++it, args...);
}
template <typename T1, typename T2>
ostream& operator<<(ostream& c, pair<T1, T2>& v) {
  c << "(" << v.first << "," << v.second << ")";
  return c;
}
template <template <class...> class TT, class... T>
ostream& operator<<(ostream& out, TT<T...>& c) {
  out << "{ ";
  for (auto& x : c) out << x << " ";
  out << "}";
  return out;
}
const int LIM = 2e5 + 5, MOD = 1e9 + 7;
const long double EPS = 1e-9;
int read() {
  int xx = 0, ff = 1;
  char ch = getchar();
  while (ch > '9' || ch < '0') {
    if (ch == '-') ff = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    xx = (xx << 3) + (xx << 1) + ch - '0';
    ch = getchar();
  }
  return xx * ff;
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int link[LIM], sz[LIM];
int find(int x) {
  if (x == link[x]) {
    return x;
  }
  return link[x] = find(link[x]);
}
void unite(int a, int b) {
  a = find(a);
  b = find(b);
  if (sz[a] < sz[b]) swap(a, b);
  link[b] = a;
  sz[a] += sz[b];
  return;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int m, n;
  cin >> m >> n;
  long long a[m], b[n];
  for (int i = 0; i < m; ++i) cin >> a[i];
  for (int i = 0; i < n; ++i) cin >> b[i];
  for (int i = 0; i < LIM; ++i) {
    link[i] = i;
    sz[i] = i;
  }
  vector<tuple<long long, int, int>> v;
  for (int i = 0; i < m; ++i) {
    int s;
    cin >> s;
    while (s--) {
      int j;
      cin >> j;
      j--;
      v.push_back({a[i] + b[j], i, j + m});
    }
  }
  sort(v.begin(), v.end(), greater<tuple<long long, int, int>>());
  long long ans = 0;
  for (auto& r : v) {
    int first, second;
    long long cost;
    tie(cost, first, second) = r;
    if (find(first) == find(second)) {
      ans += cost;
    } else {
      unite(first, second);
    }
  }
  cout << ans << '\n';
  return 0;
}
