#include <bits/stdc++.h>
//#define int long long
#define fast ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define pb push_back
using namespace std;
const int N = 65;

void solve();

signed main() {
//    fast
    int t = 1;
//  cin >> t;
    while (t--) solve();
}

const int INF = 1e9;
int ans(-INF);
int n, w[N];
struct item {
    int l, r;
} a[N];

bool cmp(item x, item y) {
    return x.l <= y.l;
}


template<typename T>
class CMP {
public:
    bool operator()(T x, T y) {
        return a[x].r > a[y].r;
    }
};

priority_queue<int, vector<int>, CMP<int>> q;

int now[N], cnt;

int now_val;

int check() {
//    cout << 1 << '\n';
    int flag(1), head(1);
    while (!q.empty())q.pop();
    for (int i = 1; i <= n; i++) {
        while (a[head].l <= now[i] && head <= n)q.push(head), head++;
        if ((!q.empty()) && a[q.top()].r < now[i]) {
            flag = 0;
        }
        if (!q.empty())q.pop();
        else flag = 0;
    }
    if (!q.empty() || head <= n)flag = 0;
    return flag;
}


void dfs(int sum, int lim) {
    if (sum == 0) {
        if (ans < now_val) {
            if (check()) {
                ans = now_val;
            }
        }
        return;
    }
    for (int i = lim; i <= sum; i++) {
        now_val += w[i];
        for (int j = 1; j <= i; j++) {
            ++cnt;
            now[cnt] = i;
        }
        dfs(sum - i, i);
        for (int j = 1; j <= i; j++)cnt--;
        now_val -= w[i];
    }
    return;
}


void solve() {
    cin >> n;
    for (int i = 1; i <= n; i++)cin >> a[i].l >> a[i].r;
    for (int i = 1; i <= n; i++)cin >> w[i];
    stable_sort(a + 1, a + n + 1, cmp);
    dfs(n, 1);
    if (ans == -INF)cout << "impossible";
    else cout << ans << '\n';
    return;
}
/*
3
2 3
1 2
2 2
4 5 100

3
1 3
3 3
2 3
1 1 100

2
1 1
2 2
1 1

3
1 2
1 2
1 2
1 100000 1

 5
1 5
1 5
1 5
1 5
1 5
-1 -1 -2 -1 -2
 */