#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N = 65;
int dp[N][N], w[N];
const int inf = 1e18 + 7;
pair<int, int> seg[N];
bitset<N> used;
signed main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    for(int i = 1; i <= n; i++){
        cin >> seg[i].second >> seg[i].first;
    }
    for(int i = 1; i <= n; i++){
        cin >> w[i];
    }
    for(int i = 0; i <= n; i++){
        for(int j = 0; j <= n; j++){
            dp[i][j] = -inf;
        }
    }
    dp[0][0] = 0;

    sort(seg + 1, seg + 1 + n);
    int ans = -inf;
    for(int i = 1; i <= n; i++){
        for(int j = i; j <= n; j++){
            for(int k = 0; k <= i; k++){
                if(dp[k][j - i] <= -1e9)
                    continue;
                int cnt = 0;
                used.reset();
                for(int t = 1; t <= n && cnt < j - i; t++){
                    if(seg[t].second <= k){
                        used[t] = 1;
                        cnt++;
                    }
                }
                cnt = 0;
                for(int t = 1; t <= n; t++){
                    if(!used[t] && seg[t].second <= i && seg[t].first >= i){
                        cnt++;
                    }
                }
                if(cnt >= i){
                    dp[i][j] = max(dp[i][j], dp[k][j - i] + w[i]);
                }
            }
        }
        ans = max(ans, dp[i][n]);
    }
    if(ans < -1e9){
        cout << "impossible\n";
    }else{
        cout << ans << '\n';
    }
}