#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
#define MAXN 65

long long read() {
    long long x = 0, f = 1;
    char c = getchar();
    while(c < 48 || c > 57) { if(c == 45) f = -1; c = getchar(); }
    while(c >= 48 && c <= 57) { x = (x << 3) + (x << 1) + (c - 48); c = getchar(); }
    return x * f;
}

long long n, w[MAXN], b[MAXN], g[MAXN], dp[MAXN], ans = -0x3f3f3f3f;
struct node { long long l, r; } a[MAXN];
bool f1 = true, f2 = true;

void update() {
    // for(int i = 1; i <= n; i ++) cout << b[i] << " ";
    // cout << ": ";
    bool flag = false;
    for(int i = 1; i <= n; i ++) g[i] = 0;
    for(int i = 1; i <= n; i ++) g[b[i]] ++;
    for(int i = 1; i <= n; i ++) 
        if(a[i].l > g[b[i]] || a[i].r < g[b[i]]) { flag = true; break; }
    // cout << flag << "\n";
    if(flag) return;
    long long res = 0;
    for(int i = 1; i <= n; i ++) res += w[g[i]];
    ans = max(ans, res);
    return;
}

void dfs(long long x) {
    if(x > n) { update(); return; }
    for(int i = 1; i <= n; i ++) 
        b[x] = i, dfs(x + 1);
    return;
}

int main() {
    n = read();
    for(int i = 1; i <= n; i ++) {
        a[i].l = read(), a[i].r = read();
        if(a[i].l != a[i].r) f1 = false;
        if(a[i].l != 1 || a[i].r != n) f2 = false;
    }
    for(int i = 1; i <= n; i ++) w[i] = read();
    if(f1) {
        bool f = false;
        for(int i = 1; i <= n; i ++) g[a[i].l] ++;
        for(int i = 1; i <= n; i ++)
            if(a[i].l != g[a[i].l]) { f = true; break; }
        if(f) { cout << "impossible\n"; return 0; }
        long long res = 0;
        for(int i = 1; i <= n; i ++) res += w[g[i]];
        cout << res << "\n";
        return 0;
    }
    if(f2) {
        for(int i = 1; i <= n; i ++) for(int j = n; j >= i; j --)
            dp[j] = max(dp[j], dp[j - i] + w[i]);
        cout << dp[n] << "\n";
        return 0;
    }
    dfs(1);
    if(ans == -0x3f3f3f3f) cout << "impossible\n";
    else cout << ans << "\n";
    return 0;
}