#include <bits/stdc++.h>
using namespace std;
const int N = 67;
const int INF = 1e9;
int n;
int ans;
int w[N];
int num[N], numst[N];
bool vis[N];
vector<int> L[N];
int tot;
int sum[N]; //sum[x] l<=x 的个数
int suf[N]; //suf[x] r>=x 的个数
auto start = chrono::high_resolution_clock::now();
void Dfs(int rmn, int mx)
{
    auto stop = chrono::high_resolution_clock::now();
    auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(stop - start).count();
    if (duration > 998) {
        cout << ans << "\n";
        exit(0);
    }
    if (n - rmn > sum[mx])
        return; //已选的(l均小于等于x) 比线段多
    if (rmn > suf[mx])
        return; //后选的(r均大于等于x) 比线段多
    if (rmn == 0) {
        //++tot;
        set<int> st;
        for (int i = 1; i <= n; ++i)
            numst[i] = 0;
        bool flag = 1;
        for (int i = 1; i <= n; ++i) {
            for (auto r : L[i]) {
                if (numst[r] == 0)
                    st.insert(r);
                ++numst[r];
            }
            for (int j = 0; j < num[i]; ++j) {
                auto it = st.lower_bound(i);
                if (it == st.end()) {
                    flag = 0;
                    break;
                } else {
                    int y = *it;
                    if (!--numst[y])
                        st.erase(it);
                }
            }
            if (!flag)
                break;
        }
        if (flag) {
            int val = 0;
            for (int i = 1; i <= n; ++i)
                val += (num[i] / i) * w[i];
            ans = max(ans, val);
        }
        return;
    }
    for (int i = mx; i <= rmn; ++i) {
        num[i] += i;
        Dfs(rmn - i, i);
        num[i] -= i;
        if (rmn <= i * 2 && rmn != i) {
            num[rmn] += rmn;
            Dfs(0, rmn);
            num[rmn] -= rmn;
            break;
        }
    }
}
void solve()
{
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        int l, r;
        cin >> l >> r;
        L[l].push_back(r);
        sum[l]++;
        suf[r]++;
    }
    for (int i = 1; i <= n; ++i)
        sum[i] += sum[i - 1];
    for (int i = n; i >= 0; --i)
        suf[i] += suf[i + 1];
    for (int i = 1; i <= n; ++i)
        cin >> w[i];
    ans = -INF;
    Dfs(n, 1);
    if (ans == -INF)
        cout << "impossible"
             << "\n";
    else
        cout << ans << "\n";

    // printf("tot = %d\n",tot);
}
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    solve();
    return 0;
}