#include<bits/stdc++.h>
using namespace std;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

    int k;
    cin >> k;
    vector<int> c(k);
    for (auto& i : c) cin >> i;
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        int x;
        cin >> x;
        x--;
        if (c[x + 1] == 0) c[x]--;
        else c[x + 1]--;
    }
    int ans = 0;
    for (auto& i : c) ans += max(0, -i);
    cout << ans;
}