#include<bits/stdc++.h>
#define int long long
using namespace std;
const int maxn=100+10;
vector <int> ver;
int inf=1e18;
int n,ans=-inf;
int vis[maxn],l[maxn],r[maxn],w[maxn];
void dfs(int x,int y){
    //cout<<x<<" "<<y<<" "<<n<<endl;
    if(x==0){
        vector <int> res(n+2,0);
        int val=0;
        for(auto u:ver){
            res[u]++;            
            val+=w[u];
        }
        int flag=1;
        for(int i=1;i<=n;i++){
            if(vis[i]<res[i]*i){
                flag=0; break;
            }
        }
        if(flag==1){
            ans=max(ans,val);
        }
        return;
    }
    for(int i=1;i<=min(x,y);i++){
        ver.push_back(i);
        dfs(x-i,i);
        ver.pop_back();
    }
}
signed main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>l[i]>>r[i];
        for(int j=l[i];j<=r[i];j++){
            vis[j]++;
        }
    }
    for(int i=1;i<=n;i++){
        cin>>w[i];
    }
    dfs(n,100);
    if(ans==-inf) cout<<"impossible\n";
    else cout<<ans<<"\n";
    return 0;
}