ATM

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;

constexpr bool typetest = 0;
constexpr int N = 5e5 + 5;
constexpr ll Inf = 1e17;

template <class T>
void read(T &x)
{
    x = 0;
    register int c;
    while ((c = getchar()) && (c > '9' || c < '0'))
        ;
    for (; c >= '0' && c <= '9'; c = getchar())
        x = x * 10 + c - '0';
}

int m, n, com[N], l(0), x[N];
ll dp[N], b[N];
int y, k;
vector<int> adj[N], nadj[N], s;
bool ck[N];

void Read()
{
    //cin >> n >> m;
    read(n), read(m);
    for (int i = 1; i <= m; ++i)
    {
        int u, v;
        //cin >> u >> v;
        read(u), read(v);
        adj[u].emplace_back(v);
        nadj[v].emplace_back(u);
    }
    m = 0;
}

void dfs(int v)
{
    ck[v] = 1;
    for (auto i : adj[v])
        if (!ck[i])
            dfs(i);
    s.emplace_back(v);
}

void dfs_com(int v)
{
    com[v] = l;
    x[++m] = v;
    for (auto i : nadj[v])
        if (!com[i])
            dfs_com(i);
}

void Kosaraju()
{
    s.reserve(n);
    for (int i = 1; i <= n; ++i)
        if (!ck[i])
            dfs(i);

    while (!s.empty())
    {
        int c = s.back();
        s.pop_back();

        if (com[c])
            continue;

        dp[++l] = -Inf;
        dfs_com(c);
    }
}

void Solve()
{
    Kosaraju();

    for (int i = 1; i <= n; ++i)
    {
        ll v;
        read(v);
        b[com[i]] += v;
    }

    read(y), read(k);
    y = com[y];
    dp[y] = b[y];

    for (int i = 1; i <= n; ++i)
        for (auto t : nadj[x[i]])
            if (com[t] != com[x[i]])
                dp[com[x[i]]] = max(dp[com[x[i]]], dp[com[t]] + b[com[x[i]]]);

    ll ans(-Inf);

    for (int i = 1; i <= k; ++i)
    {
        int v;
        read(v);
        ans = max(ans, dp[com[v]]);
    }
    cout << ans;
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t(1);
    if (typetest)
        cin >> t;
    for (int _ = 1; _ <= t; ++_)
    {
        //cout << "Case #" << _ << "\n";
        Read();
        Solve();
    }
}