#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define OPFI(x) freopen(#x".in", "r", stdin);\
                freopen(#x".out", "w", stdout)
#define REP(i, a, b) for(int i=(a); i<=(b); ++i)
#define REPd(i, a, b) for(int i=(a); i>=(b); --i)
inline ll rd(){
    ll r=0, k=1; char c; while(!isdigit(c=getchar())) if(c=='-') k=-k;
    while(isdigit(c)) r=r*10+c-'0', c=getchar(); return r*k;
}
ll n, w[70], ans=-LLONG_MAX/2;
#define MP make_pair
#define L first
#define R second
#define PII pair<int, int>
PII r[70];
vector<int> st;
int tmp[70];
void dfs(int s, int low){
    if(s==n){
        REP(i, 1, n) tmp[i]=0;
        for(int i:st) tmp[i]+=i;
        int j=1, flag=true;
        REP(i, 1, n){
            while(j<=n&&tmp[j]==0) ++j;
            if(r[i].L<=j&&j<=r[i].R) --tmp[j];
            else flag=false;
        }
        if(flag){
            ll sum=0;
            for(int i:st) sum+=w[i];
            ans=max(ans, sum);
        }
        return;
    }
    REP(i, low, n-s){
        st.push_back(i);
        dfs(s+i, i);
        st.pop_back();
    }
}
int main(){
    n=rd();
    REP(i, 1, n) r[i].L=rd(), r[i].R=rd();
    REP(i, 1, n) w[i]=rd();
    sort(r+1, r+n+1);
    dfs(0, 1);

    if(ans==-LLONG_MAX/2) puts("impossible");
    else printf("%lld\n", ans);
    return 0;
}