#include "bits/stdc++.h"

using namespace std;

using ll = long long;
using ld = long double;

#define l first
#define r second
#define all(x) (x).begin(), (x).end()

const int M = 77;
const int inf = 1e9;

int d[M][M];

void uax(int &x, int y) {
  x = max(x, y);
}

int main() {
#ifndef ONLINE_JUDGE
  freopen("e.in", "r", stdin);
#endif
  ios_base::sync_with_stdio(false);

  int n;
  cin >> n;
  vector<int> l(n), r(n);
  for (int i = 0; i < n; ++i)
    cin >> l[i] >> r[i];

  sort(all(l));
  sort(all(r));

  vector<int> w(n + 1);
  for (int i = 1; i <= n; ++i)
    cin >> w[i];

  for (int i = 0; i < M; ++i)
    for (int j = 0; j < M; ++j)
      d[i][j] = -inf;

  for (int j = 0; j < M; ++j)
    d[j][0] = 0;

  for (int k = 1; k <= n; ++k)
    for (int s = 0; s <= n; ++s) {
      if (d[k][s] == -inf)
        continue;

      uax(d[k + 1][s], d[k][s]);

      if (s + k <= n) {
        bool can = true;
        for (int i = s; i < s + k; ++i)
          can &= l[i] <= k && k <= r[i];
        if (can)
          uax(d[k][s + k], d[k][s] + w[k]);
      }
    }

  int ans = d[n][n];
  if (ans > -inf)
    cout << ans << "\n";
  else
    cout << "impossible\n";

  return 0;
}