/*
非递归tarjan要爆栈，实用性不是很强，需要用网上的这个非递归版tarjan
*/
#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
using namespace std;
const int maxn = 500500;
struct edge{
    int v;
    int nxt;
}e[maxn];
int n,m,s,p,mny[maxn],nmny[maxn];
int head[maxn],cnt;
int stop,sta[maxn],dfn[maxn],low[maxn],isin[maxn],indx;
int tot;
int d[maxn],vis[maxn];
bool inst[maxn];
stack<int> st;
vector<int> g[maxn];
int read(){
    char ch=getchar();
    int x=0,f=1;
    while(!(ch>=‘0‘&&ch<=‘9‘)){if(ch==‘-‘)f=-1;ch=getchar();};
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+(ch-‘0‘);ch=getchar();};
    return x*f;
}
void ins(int u,int v){
    cnt++;
    e[cnt].v = v;
    e[cnt].nxt = head[u];
    head[u] = cnt;
}
void input(){
    n = read();
    m = read();
    int u,v;
    for(int i = 1;i <= m;i++){
        u = read();
        v = read();
        ins(u,v);
    }
    for(int i = 1;i <= n;i++) mny[i] = read();
    s = read();
    p = read();
}
void st_psh(int x){
    dfn[x] = low[x] = ++indx;
    inst[x] = true;
    sta[++stop] = x;
    st.push(x);
}
void tarjan(int x){
    int t;
    st_psh(x);
    while(!st.empty()){
        t = st.top();
        for(int i = head[t];i;i = e[i].nxt){
            if(dfn[e[i].v] == 0){
                st_psh(e[i].v);
                break;
            }
        }
        if(t == st.top()){
            for(int i = head[t];i;i = e[i].nxt){
                if(dfn[e[i].v] > dfn[t]) low[t] = min(low[e[i].v],low[t]);
                else if(inst[e[i].v]){low[t] = min(dfn[e[i].v],low[t]);}
            }
            if(dfn[t] == low[t]){
                ++tot;
                int j;
                do{
                    j = sta[stop--];
                    inst[j] = false;
                    isin[j] = tot;
                    nmny[tot] += mny[j];
                }while(j != t);
            }
            st.pop();
        }
    }
}
void spfa(){
    int u,to;
    queue<int> q;
    u = isin[s];
    d[isin[s]] = nmny[isin[s]];
    vis[isin[s]] = true;
    q.push(isin[s]);
    while(!q.empty()){
        u = q.front();
        q.pop();
        for(int i = 0;i < g[u].size();i++){
            to = g[u][i];
            if(d[to] < d[u] + nmny[to]){
                d[to] = d[u] + nmny[to];
                if(!vis[to]){
                    vis[to] = true;
                    q.push(to);
                }
            }
        }
        vis[u] = false;
    }
}
void work(){
    for(int i = 1;i <= n;i++){
        if(!dfn[i]) tarjan(i);
    }
    for(int i = 1;i <= n;i++){
        for(int j = head[i];j;j = e[j].nxt){
            if(isin[i] != isin[e[j].v]){
                g[isin[i]].push_back(isin[e[j].v]);
                //cout<<isin[i]<<" "<<isin[e[j].v]<<endl;
            }
        }
    }
    spfa();
    int qs,ans = 0;
    while(p--){
        qs = read();
        ans = max(d[isin[qs]],ans);
    }
    cout<<ans;
}
int main(){
    input();
    work();
    return 0;
}