#include<bits/stdc++.h>
#define vectorwyx maze
namespace vectorwyx{
#define pii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define mk make_pair
#define sml(x,y) (x=min(x,y))
#define big(x,y) (x=max(x,y))
#define ll long long
#define uint unsigned
#define ull unsigned long long
#define umap unordered_map
#define db double
#define fo(i,x,y) for(int i=(x);i<=(y);++i)
#define go(i,x,y) for(int i=(x);i>=(y);--i)
#define ptc putchar
#define gtc getchar
#define emp emplace
#define re return
#define co continue
#define brk break
#define HH (ptc('\n'))
#define bctz __builtin_ctzll
#define bclz __builtin_clz
#define bppc __builtin_popcount
using namespace std;
ll seed=chrono::system_clock::now().time_since_epoch().count();
mt19937 rnd(seed);
inline int rm(int x,int y){return (int)(rnd()%(y-x+1ll)+x);}
inline int read(){signed ch=getchar();int x=0,f=1;while(!isdigit(ch)){if(ch==(int)('-'))f=-1;ch=getchar();}while(isdigit(ch)){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}return x*f;}
template<typename T> void out(T *a,int l,int r){fo(i,l,r) cout<<*(a+i)<<' ';puts("");}

const int N=100,inf=1e9;
namespace Heap{
int c[N];
ull sts;
void clear(){memset(c,0,sizeof c);sts=0;}
void push(int x){
    // printf("push(%d)\n",x);
    if(!c[x]) sts|=1ll<<x;
    c[x]++;
}
int top(){re __builtin_ctzll(sts);}
bool pop(int k){
    // printf("pop(%d)\n",k);
    while(k){
        if(!sts) re 0;
        int x=top();
        if(c[x]>k){c[x]-=k;re 1;}
        k-=c[x],c[x]=0;
        sts^=1<<x;
    }
    re 1;
}
}
int l[N],r[N],w[N],n,c[N],ans=-inf;
vector<int> g[N];

void play(){
    Heap::clear();
    // cout<<"play:";out(c,1,n);
    fo(i,1,n){
        for(int j:g[i]) Heap::push(j);
        if(!Heap::pop(c[i]*i)) re;
        if(Heap::top()<=i) re;
    }
    int val=0;
    fo(i,1,n) val+=w[i]*c[i];
    big(ans,val);
}   

void dfs(int id,int res){
    // printf("dfs(%d,%d)\n",id,res);
    if(res==0){play();re;}
    if(res<id) re;
    if(id>n) re;
    dfs(id+1,res);
    fo(i,1,res/id){
        res-=id;
        c[id]=i;
        dfs(id+1,res);
    }
    c[id]=0;
}

signed main(){
    cin>>n;
    fo(i,1,n) l[i]=read(),r[i]=read(),g[l[i]].pb(r[i]);
    fo(i,1,n) w[i]=read();
    dfs(1,n);
    if(ans==-inf) cout<<"impossible";
    else cout<<ans;
    return 0;
}
}
/*
3
2 3
1 2
2 2
4 5 100
-------------------------------------------------
*/










signed main(){re vectorwyx::main();}