#include <bits/stdc++.h>
#define int long long
using namespace std;
int l[100], r[100];
int b[100], a[100];
int n;
int dp[100];
int calc(void){
	for(int i=1;i<=n;i++) dp[i] = 0;
	for(int i=1;i<=n;i++){
		int mx = r[b[i]], mn = l[b[i]];
		dp[i] = -1e15;
		for(int j=i-1,k=1;j>=0;j--,k++){
			if(mn <= k && k <= mx){
				dp[i] = max(dp[i], dp[j] + a[k]);
			}
			mx = min(mx, r[b[j]]);
			mn = max(mn, l[b[j]]);
		}
	}
//	for(int i=1;i<=n;i++) cout << dp[i] << ' ';cout<<endl;
//	cout<<endl;
	return dp[n];
}
signed main(){
	cin>>n;
	for(int i=1;i<=n;i++)cin>>l[i]>>r[i];
	for(int i=1;i<=n;i++)cin>>a[i];
	double t = 100000000, tmd = 0.993; int ans = -1e15, res = -1e15;
	for(int i=1;i<=n;i++) b[i] = i;
	random_shuffle(b+1,b+n+1);
	mt19937 rnd(time(0));
	while(t>=1e-13){
		int r = rnd()%(n-1)+2, l = rnd()%(r-1)+1;
		swap(b[l], b[r]);
		int tmp = calc();
		if(tmp > ans){
			ans = tmp;
		}
		else if(double(rnd()) <= exp(double(tmp - ans) / t) * double(1LL<<32)){
			ans = tmp;
		}
		else{
			swap(b[l], b[r]);
		}
		res = max(res, ans);
		t *= tmd;
	}
	if(res < -1e15)cout << "impossible";
	else cout << res << endl;
}