#include <bits/stdc++.h>
using namespace std;

int n;
pair<int,int> ve[100];
int w[100];
int sz;
int vec[70];
int ans=0;
int cal[70];
bool check()
{
    long long qu=0;
    for(int i=0,now=0;i<sz;i++){
        while(now<n&&ve[now].first<=vec[i]){
            cal[ve[now].second]++;
            qu|=1ll<<ve[now].second;
            now++;
        }
        int x=vec[i],y=vec[i];
        while(y--){
            if(qu==0)return false;
            int z=__builtin_ctzll(qu);
            if(--cal[z]==0)qu^=1ll<<z;
            if(x>z)return false;
        }
    }
    while(qu){
        int z=__builtin_ctzll(qu);
        cal[z]=0;
    }
    return true;
}
int nowsum=0;
void dfs(int x,int cur, int n) {
    if (cur == n) {
        // for(auto it:vec)cout<<it<<" ";;cout<<"\n";
        
        if (nowsum <= ans) {
            return;
        }
        if (check()) {
            ans = nowsum;
        }
        
        return ;
    }
    if(cur>n)return ;
    for (int i = x; i<=n-cur; i++) {
        vec[sz++] = i;
        nowsum+=w[i];
        dfs(i,cur + i, n);
        --sz;
        nowsum-=w[i];
    }

}


int main() {

    std::cin >> n;
    for(int i=1;i<=n;i++){
        int l,r;cin>>l>>r;
        ve[i-1]=make_pair(l,r);
    }
    sort(ve,ve+n);
    for(int i=1;i<=n;i++)cin>>w[i];
    int inf=1e9;
    ans=-inf;
    dfs(1,0,n);
    if(ans!=-inf)std::cout << ans << std::endl;
    else cout<<"impossible\n";
}