#include <bits/stdc++.h>
using namespace std;

int main() {
	cin.tie(0)->sync_with_stdio(0);

	int n; cin >> n;
	vector<pair<int,int>> students(n); for (auto &[l, r] : students) cin >> l >> r, l--, r--; ranges::sort(students);
	vector<int> w(n); for (auto &x : w) cin >> x;
	
	set<vector<int>> s {vector<int>(n)};
	for (auto [l, r] : students) {
		set<vector<int>> t;
		
		for (auto x : s) {
			int last = n-1;
			while (last and not x[last]) last--;

			if (x[last] % (last+1)) {
				x[last]++;
				t.emplace(x);
			} else {
				l = max(l, last);
				while (l <= r) {
					x[l]++;
					t.emplace(x);
					x[l]--;
					l++;
				}
			}
		}
		s = std::move(t);
	}

	long long mx = LLONG_MIN;
	for (auto x : s) {
		long long sum = 0;
		bool ok = 1;
		for (int i = 0; i < n; i++) sum += 1LL * x[i]/(i+1) * w[i], ok &= x[i] % (i+1) == 0;
		if (ok) mx = max(mx, sum);
	}
	if (mx == LLONG_MIN) cout << "impossible\n";
	else cout << mx << '\n';
}