#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e5 + 5;
int n, k;
long long c[MAX], totals[MAX];
bool vis[MAX];

int main() {
    ios::sync_with_stdio(false);
    cin >> n >> k;
    for (int i = 0; i < n; i++)
        cin >> c[i];
    long long res = 0, total = 0;
    for (int i = 0; i < n; i++) {
        total += c[i];
        res += c[i] * c[(i + 1) % n];
    }
    for (int i = 0; i < k; i++) {
        long long cap; cin >> cap;
        cap--;
        vis[cap] = true;
        total -= c[cap];
        long long cur = total;
        if (!vis[(cap + 1) % n])
            cur -= c[(cap + 1) % n];
        if (!vis[(cap > 0 ? cap - 1 : n - 1)])
            cur -= c[(cap > 0 ? cap - 1 : n - 1)];
        res += cur * c[cap];
    }
    cout << res;
}