#include<cstdio>
#include<iostream>
#include<vector>
#define RI register int
#define CI const int&
using namespace std;
const int N=65,INF=1e9;
int n,cnt,l[N],r[N],L[N],R[N],w[N],vis[N],mat[N],ans=-INF; vector <int> vec,v[N];
inline bool find(CI now,CI idx)
{
    for (auto to:v[now]) if (vis[to]!=idx)
    {
        vis[to]=idx;
        if (!mat[to]||find(mat[to],idx))
        return mat[to]=now,1;
    }
    return 0;
}
inline int calc(vector <int>& vec)
{
    ++cnt;
    //for (auto x:vec) printf("%d ",x); putchar('\n');
    int res=0; for (auto x:vec) res+=w[x];
    if (res<ans) return -INF;
    int tot=0; for (RI i=0;i<vec.size();++i)
    L[i+1]=tot+1,tot+=vec[i],R[i+1]=tot;
    for (RI i=1;i<=n;++i) v[i].clear();
    for (RI i=1;i<=n;++i)
    {
        int lp=-1,rp=-1;
        for (RI j=0;j<vec.size();++j)
        if (vec[j]>=l[i]) { lp=j+1; break; }
        for (RI j=(int)vec.size()-1;j>=0;--j)
        if (vec[j]<=r[i]) { rp=j+1; break; }
        if (lp==-1||rp==-1) return -INF;
        for (RI j=lp;j<=rp;++j)
        for (RI k=L[j];k<=R[j];++k) v[i].push_back(k);
    }
    for (RI i=1;i<=n;++i) vis[i]=mat[i]=0;
    for (RI i=1;i<=n;++i) if (!find(i,i)) return -INF;
    return res;
}
inline void DFS(vector <int>& vec,CI sum,CI lst)
{
    if (sum==n) return (void)(ans=max(ans,calc(vec)));
    for (RI i=lst;i<=n-sum;++i) vec.push_back(i),DFS(vec,sum+i,i),vec.pop_back();
}
int main()
{
    scanf("%d",&n);
    for (RI i=1;i<=n;++i) scanf("%d%d",&l[i],&r[i]);
    for (RI i=1;i<=n;++i) scanf("%d",&w[i]);
    DFS(vec,0,1);
    //printf("count  = %d\n",cnt);
    if (ans==-INF) puts("impossible"); else printf("%d",ans);
    return 0;
}