#include <bits/stdc++.h>

#define x first
#define y second
#define el '\n'
#define debug(x) cerr << #x << ": " << x << endl
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int N = 3e5 + 10, INF = 0x3f3f3f3f, mod = 998244353;

int n, w[N];
vector<pii> seg;
vector<int> stk;
int ans = -INF * 2;

void dfs(int lst, int tot) {
    if (tot > n) return;
    if (tot == n) {
        int i = 0, res = 0;
        int ok = 1;
        vector<int> cnt(n + 1);
        ll s = 0;
        for (int sz: stk) {
            while (i < n && seg[i].x <= sz) {
                ++cnt[seg[i].y];
                s |= 1ll << seg[i++].y;
            }
            for (int i = 0; i < sz; ++i) {
                if (!s) {
                    ok = 0;
                    break;
                }
                int t = __builtin_ctz(s);
                if (t < sz) {
                    ok = 0;
                    break;
                }
                --cnt[t];
                if (!cnt[t]) s ^= 1ll << t;
            }
            res += w[sz];
            if (!ok) break;
        }
        if (ok) ans = max(ans, res);
        return;
    }
    for (int j = lst; j + tot <= n; ++j) {
        stk.emplace_back(j);
        dfs(j, tot + j);
        stk.pop_back();
    }
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> n;
    seg.resize(n);
    for (int i = 0; i < n; ++i) cin >> seg[i].x >> seg[i].y;
    sort(seg.begin(), seg.end());
    for (int i = 1; i <= n; ++i) cin >> w[i];
    dfs(1, 0);
    if (ans < -INF) cout << "impossible\n";
    else cout << ans << el;
}