#include <bits/stdc++.h>
using namespace std;
int n, k;
vector<pair<long long, long long> > nums;
int main() {
  cin >> n;
  nums.resize(n);
  for (int i = 0; i < n; i++) {
    long long a, b;
    cin >> a >> b;
    nums[i] = make_pair(b, a);
  }
  sort(nums.begin(), nums.end());
  long long res = 0;
  long long left;
  long long fac = 1;
  long long last_left = 0;
  cin >> k;
  vector<long long> ks(k + 1);
  for (int i = 0; i < k; i++) cin >> ks[i];
  ks[k] = -1;
  long long k_cnt = 0;
  left = ks[0];
  for (int i = 0; i < n; i++) {
    if (left == -1) {
      res += fac * nums[i].second * nums[i].first;
      continue;
    }
    if (left <= nums[i].second) {
      res += fac * left * nums[i].first;
      nums[i].second -= left;
      i--;
      k_cnt++;
      if (ks[k_cnt] == -1)
        left = -1;
      else
        left = (ks[k_cnt] - ks[k_cnt - 1]);
      fac++;
    } else {
      res += fac * nums[i].second * nums[i].first;
      left -= nums[i].second;
      nums[i].second = 0;
    }
  }
  cout << res;
  return 0;
}
