// Hallelujah, praise the one who set me free
// Hallelujah, death has lost its grip on me
// You have broken every chain, There's salvation in your name
// Jesus Christ, my living hope
#include <bits/stdc++.h> 
using namespace std;

#define REP(i, s, e) for (int i = (s); i < (e); i++)
#define RREP(i, s, e) for (int i = (s); i >= (e); i--)
template <class T>
inline bool mnto(T& a, T b) {return b < a ? a = b, 1 : 0;}
template <class T>
inline bool mxto(T& a, T b) {return a < b ? a = b, 1: 0;}

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
#define FI first
#define SE second
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
typedef tuple<int, int, int> iii;
#define ALL(_a) _a.begin(), _a.end()
#define SZ(_a) (int) _a.size()
#define pb push_back
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;
typedef vector<iii> viii;

#ifndef DEBUG
#define cerr if (0) cerr
#endif

const int INF = 1000000005;
const ll LINF = 1000000000000000005ll;
const int MAXN = 65;

int n;
int l[MAXN], r[MAXN];
int w[MAXN];

unordered_map<ll, int> memo;
int solve(ll msk) {
    if (msk == 0) {
        return 0;
    }
    if (memo.find(msk) != memo.end()) {
        return memo[msk];
    }
    vi ev[n + 1];
    REP (i, 0, n) {
        if (msk >> i & 1) {
            ev[r[i]].pb(i);
            ev[l[i] - 1].pb(~i);
        }
    }
    set<ii> st;
    int res = -INF;
    RREP (i, n, 1) {
        for (auto id : ev[i]) {
            if (id >= 0) {
                st.insert({-l[id], id});
            } else {
                id = ~id;
                st.erase(st.find({-l[id], id}));
            }
        }
        ev[i].clear();
        if (SZ(st) >= i) {
            int nmsk = msk, cnt = 0;
            for (auto [_, id] : st) {
                if (cnt++ == i) {
                    break;
                }
                nmsk ^= 1 << id;
            }
            int tmp = solve(nmsk);
            if (tmp != -INF) {
                mxto(res, tmp + w[i]);
            }
        }
    }
    ev[0].clear();
    return memo[msk] = res;
}

int main() {
#ifndef DEBUG
    ios::sync_with_stdio(0), cin.tie(0);
#endif
    cin >> n;
    REP (i, 0, n) {
        cin >> l[i] >> r[i];
    }
    REP (i, 1, n + 1) {
        cin >> w[i];
    }
    int ans = solve((1ll << n) - 1);
    if (ans == -INF) {
        cout << "impossible\n";
    } else {
        cout << ans << '\n';
    }
}