#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

vector<int> group;
vector<pair<int, int>> a;
vector<int> w;
int ans;

bool check() {
	vector<int> cnt = group;
	int n = group.size(), m = a.size();
	for (int i = 0, j = 0, k; i < n; ++i)
	{
		k = cnt[i];
		while (k--)
		{
			auto &[l, r] = a[j];
			if (l > cnt[i] || r < cnt[i]) return 0;
			++j;
		}
	}
	return 1;
}


void dfs(int cur, int step) {
	if (cur == 0) {
		if (!check()) return;
		int sum = 0;
		for (auto x : group) sum += w[x - 1];
		ans = max(ans, sum);
		return;
	}
	for (int i = step; i <= cur; i++) {
		group.push_back(i);
		dfs(cur - i, i);
		group.pop_back();
	}
}

int main() {
	int n; cin >> n;
	a.resize(n);
	w.resize(n);
	ans = -2e9;
	for (auto &[l, r] : a) cin >> l >> r;
	for (auto &x : w) cin >> x;
	sort(a.begin(), a.end(), [](const auto &x, const auto &y) {
		return x.second < y.second;
	});
	dfs(n, 1);
	if (ans != -2e9) cout << ans << '\n';
	else cout << "impossible\n";
	return 0;
}