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

const int inf = 1e9;
const int N = 100;

int n;
pair<int, int> t[N + 1];
int w[N];

vector<int> a;

int ans = -inf;
priority_queue<int, vector<int>, greater<>> pq;

int ti;

inline char nc() {
    static char buf[1000000], *p1 = buf, *p2 = buf;
    return p1 == p2 && (p2 = (p1 = buf) + fread (buf, 1, 1000000, stdin), p1 == p2) ? EOF : *p1++;
}

// #define nc getchar
inline void read(int &sum) {
    char ch = nc();
    int tf = 0;
    sum = 0;
    while((ch < '0' || ch > '9') && (ch != '-')) ch = nc();
    tf = ((ch == '-') && (ch = nc()));
    while(ch >= '0' && ch <= '9') sum = sum * 10+ (ch - 48), ch = nc();
    (tf) && (sum =- sum);
}

void dfs(int sum) {
	// if (clock() - ti >= CLOCKS_PER_SEC * 0.9) {
	// 	if (ans == -inf) {
	// 		cout << "impossible\n";
	// 	} else {
	// 		cout << ans << "\n";
	// 	}
	// 	exit(0);	
	// }
	if (sum == 0) {
		int j = 0;
		for (int k = (int)a.size() - 1; k >= 0; k--) {
			int sz = a[k];
			while (j + 1 <= n && t[j + 1].first <= sz) {
				j++;
				pq.push(t[j].second);
			}
			for (int i = 1; i <= sz; i++) {
				if (pq.empty() || pq.top() < sz) {
					while (!pq.empty()) {
						pq.pop();
					}
					return;
				}
				pq.pop();
			}
		}

		int val = 0;
		for (auto sz : a) {
			val += w[sz];
		}
		ans = max(ans, val);

		return;	
	}

	if (sum == n) {
		for (int i = 1; i <= n; i++) {
			a.push_back(i);
			dfs(sum - i);
			a.pop_back();
		}
		return;
	}

	int lst = a.back();
	for (int i = 1; i <= min(lst, sum); i++) {
		a.push_back(i);
		dfs(sum - i);
		a.pop_back();
	}
}

signed main() {  
    ios::sync_with_stdio(false);
    cin.tie(nullptr);  

	ti=clock();
    
    read(n);

	for (int i = 1; i <= n; i++) {
		read(t[i].first);
		read(t[i].second);
	}
	sort(t + 1, t + n + 1);

	for (int i = 1; i <= n; i++) {
		read(w[i]);
	}

	dfs(n);

	if (ans == -inf) {
		cout << "impossible\n";
	} else {
		cout << ans << "\n";
	}

    return 0;
}