// 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;
ii lr[MAXN];
int w[MAXN];

map<pll, int> memo;
int solve(ll msk, int d) {
    if (d == 0) {
        return -INF;
    }
    if (msk == 0) {
        return 0;
    }
    if (memo.find({msk, d}) != memo.end()) {
        return memo[{msk, d}];
    }
    int cnt = 0, nmsk = msk;
    REP (i, 0, n) {
        if ((msk >> i & 1) && lr[i].FI <= d && d <= lr[i].SE) {
            nmsk ^= 1 << i;
            if (++cnt == d) {
                break;
            }
        }
    }
    int res = solve(msk, d - 1);
    if (cnt == d) {
        int tmp = solve(nmsk, d);
        if (tmp != -INF) {
            mxto(res, solve(nmsk, d) + w[d]);
        }
    }
    return memo[{msk, d}] = res;
}

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