#include<bits/stdc++.h>

int main() {
	int n;
	std::cin >> n;
	std::vector<std::pair<int, int>> seg(n);
	for (int i = 0; i < n; ++i) {
		std::cin >> seg[i].first >> seg[i].second;
	}
	std::sort(seg.begin(), seg.end(), [&](auto x, auto y) {
		return x.second < y.second;
	});
	// for (auto [l, r] : seg) std::cout << l << ' ' << r << std::endl;
	std::map<int64_t, int> mp;
	mp[0] = 0;
	for (int i = 1; i <= n; ++i) {
		int w;
		std::cin >> w;
		std::priority_queue<std::pair<int, int64_t>, std::vector<std::pair<int, int64_t>>, std::greater<std::pair<int, int64_t>>> pq;
		for (auto [x, y] : mp) pq.emplace(y, x);
		while (pq.size()) {
			auto [val, msk] = pq.top();
			pq.pop();
			if (mp[msk] < val) continue;
			int64_t add = 0;
			for (int j = 0; j < n && __builtin_popcountll(add) < i; ++j) {
				if ((~msk >> j & 1) && seg[j].first <= i && i <= seg[j].second) add |= 1ll << j;
			}
			if (__builtin_popcountll(add) == i) {
				// std::cout << i << ' ' << msk << ' ' << add << ' ' << val + w << std::endl;
				msk |= add;
				val += w;
				if (!mp.count(msk) || mp[msk] > val) {
					mp[msk] = val;
					pq.emplace(val, msk);
				}
			}
		}
	}
	int64_t fin = (1ll << n) - 1;
	if (!mp.count(fin)) std::cout << "impossible";
	else std::cout << mp[fin];
}