#pragma GCC optimize(3)
#include <bits/stdc++.h>
using namespace std;
#define rep(i,j,k) for(i=j;i<=k;++i)
#define dow(i,j,k) for(i=j;i>=k;--i)
#define pr pair
#define mkp make_pair
#define fi first
#define se second
const int N=70;
int cnt[N],n,w[N],ans=1<<31,acc[N];
vector<pr<int,int > >st[N],ed[N];
void dfs(int s,int n,int cur){
    if(s==n){
        int i,j,flg=1;
        //set<pr<int,int> >S;
        rep(i,1,cur){
            if(acc[i]<cnt[i]*i){flg=0;break;}
        }
        if(flg){
            int sum=0;
            //cerr<<"ok:";
            rep(i,1,cur)sum+=cnt[i]*w[i];//,cerr<<i<<' '<<cnt[i]<<'\n';
            ans=max(ans,sum);
        }
        return;
    }
    if(s+cur>n)return;
    int i;
    for(i=0;i*(cur+1)+s<=n;++i){
        cnt[cur+1]=i;
        dfs(s+i*(cur+1),n,cur+1);
    }
}
int main(){//freopen("in.txt","r",stdin);
    ios::sync_with_stdio(false);
    cin>>n;
    int i,j;
    rep(i,1,n){
        int l,r;cin>>l>>r;
        st[l].push_back(mkp(r,i));ed[r].push_back(mkp(r,i));
        rep(j,l,r)acc[j]++;
    }
    rep(i,1,n)cin>>w[i];
    dfs(0,n,0);
    if(ans>(1<<31))cout<<ans;else cout<<"impossible";
}