#include<bits/stdc++.h>
#define int long long
#define endl '\n'
#define inf 0x3f3f3f3f
#define pb push_back
#define fi first
#define se second
#define pii pair<int,int>
using namespace std;
const int maxn=2e5+10;
int ans=-inf; 
int n;
struct node{
   int l,r,id;
   bool operator <(const node &other) const
   {
      return r>other.r;
   }
}a[66];
vector<node> b[66];
int w[66],c[66];
int su=0;
bool check(int cnt)
{
    priority_queue<node> q;
    int add=1;
    for(int i=1;i<=cnt;i++)
	{
	   while(add<=c[i])
	   {
	       for(auto p:b[add])
	       q.push(p);
	       add++;
	   }
	   if(q.top().r<c[i]) return 0;
	   
	   if(q.size()<c[i]) return 0;
	   
	   for(int j=1;j<=c[i];j++) q.pop();
	
	} 
    
	return 1;
}
void dfs(int sum,int cnt)
{
    if(sum==n)
    {
//        for(int i=1;i<=cnt;i++)
//        cout<<c[i]<<" ";cout<<endl;
        int res=0;
        for(int i=1;i<=cnt;i++)
		res+=w[c[i]];
        if(res>ans)
        {
		    if(check(cnt))
            ans=res;
            return;
		}
	}
	for(int i=c[cnt];i+sum<=n;i++)
	{
	    c[cnt+1]=i;
	    dfs(sum+i,cnt+1); 
	}
}
void kakakaa()
{
    cin>>n;
    for(int i=1;i<=n;i++)
    cin>>a[i].l>>a[i].r,a[i].id=i,b[a[i].l].pb(a[i]);
    c[0]=1;
    
    for(int i=1;i<=n;i++)
    cin>>w[i];
	dfs(0,0);
	if(ans==-inf)
	cout<<"impossible";
	else
    cout<<ans;
    
    //cout<<endl<<su;
}
signed main()
{
   ios::sync_with_stdio(false);//解除cin和cout的绑定，让它们可以独立缓冲
   cin.tie(0);
   cout.tie(0);
   kakakaa();
   return 0;
}