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

#define ll long long
#define ull unsigned long long
#define INF 0x3f3f3f3f3f3f3f3f

void solve()
{
    int n;
    cin >> n;
    vector<pair<int, int>> pr(n);
    for (int i = 0; i < n; i++)
    {
        cin >> pr[i].first >> pr[i].second;
    }
    vector<int> w(n + 1);
    for (int i = 1; i <= n; i++)
    {
        cin >> w[i];
    }
    sort(pr.begin(), pr.end(), [&](const pair<int, int>& a, const pair<int, int>& b)
    {
        if(a.second != b.second)
            return a.second < b.second;
        return a.first < b.first;
    });
    map<ll, ll> dp;
    dp[(1ll << n) - 1] = 0;
    ll lst = INF;
    while (lst != 0)
    {
        auto it = dp.lower_bound(lst);
        if(it == dp.begin())
            break;
        it = prev(it);
        auto [state, val] = *it;
        if(state == 0)
            break;
        // cerr << "state=" << state << " val=" << val << endl;
        int biggest = 0;
        for (int i = 0; i < n; i++)
        {
            if(state >> i & 1)
                biggest = i;
        }
        int bl = pr[biggest].first, br = pr[biggest].second;
        for (int x = bl; x <= br; x++)
        {
            vector<pair<int, int>> temp;
            for (int i = 0; i < n; i++)
            {
                if (!(state >> i & 1))
                    continue;
                if (i == biggest)
                    continue;
                if(pr[i].second >= x)
                    temp.push_back({pr[i].first, i});
            }
            sort(temp.begin(), temp.end(), greater<pair<int, int>>());
            if(temp.size() < x - 1)
                continue;
            ll newstate = state ^ (1ll << biggest);
            for (int i = 0; i < x - 1; i++)
            {
                newstate ^= (1ll << temp[i].second);
            }
            if(dp.contains(newstate))
                dp[newstate] = max(dp[newstate], val + w[x]);
            else
                dp[newstate] = val + w[x];
        }
        lst = state;
    }
    if(!dp.contains(0))
        cout << "impossible\n";
    else
        cout << dp[0] << '\n';
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int t = 1;
    // cin >> t;
    while (t--)
    {
        solve();
    }
}