// https://www.youtube.com/watch?v=R0P_f0gXXqs
// I could feel your heartbeat
// I could feel somewhere you’re looking down
// ‘Cause it’s you who I’m loving
// And it’s you that I want in need

#ifndef ONLINE_JUDGE
#include "templates/debug.hpp"
#else
#define debug(...)
#endif

#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using u64 = uint64_t;

#define int i64
constexpr int INF = 1e18;
void solve() {
    int n; cin >> n;
    struct Seg {
        int l, r;
        bool operator<(const Seg& o) const {
            return r < o.r;
        }
    };
    vector<Seg> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i].l >> a[i].r;
    }
    sort(a.begin(), a.end());
    vector<int> w(n + 1);
    for (int i = 1; i <= n; i++) {
        cin >> w[i];
    }
    // partitions
    vector<int> p;
    int now_w = 0;
    int ans = -INF;
    function<void(int, int)> dfs = [&](int sum, int last) {
        if (sum == n) {
            vector<int> c = p;
            int g = p.size(), l = 0;
            for (int i = 0; i < n; i++) {
                while (l < g && !c[l]) l++;
                if (p[l] < a[i].l || p[l] > a[i].r) return;
                else c[l]--;
            }
            ans = max(ans, now_w);
            return;
        }
        for (int x = last; x + sum <= n; x++) {
            if (x + sum != n && x + x + sum > n) continue;
            now_w += w[x];
            p.push_back(x);
            dfs(sum + x, x);
            now_w -= w[x];
            p.pop_back();
        }
    };
    dfs(0, 1);
    if (ans == -INF) {
        cout << "impossible\n";
    } else cout << ans << "\n";
}
#undef int

// Make bold hypotheses and verify carefully
int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    };
}