#include<stdio.h>
#include<stack>
#include<queue>
#include<algorithm>
using namespace std;
const int mxn=510000;
struct Edge {int to,next;
}e[mxn<<1],E[mxn<<1];
int n,m,cnt,idx,tot,st,k,ans;
int first[mxn<<1],dfn[mxn],low[mxn],w[mxn],W[mxn],bel[mxn],dis[mxn],head[mxn<<1];
bool ins[mxn],vis[mxn];
stack<int> stk;
queue<int> q;
void add(int from,int to) {e[++cnt].to=to;e[cnt].next=first[from];first[from]=cnt;
}void Tarjan(int x)
{dfn[x]=low[x]=++idx;ins[x]=1;stk.push(x);for(int i=first[x];i;i=e[i].next) {int to=e[i].to;if(!dfn[to]) {Tarjan(to);low[x]=min(low[x],low[to]);} else if(ins[to]) low[x]=min(low[x],dfn[to]);}if(low[x]==dfn[x]) {tot++;int top;do {top=stk.top();stk.pop();ins[top]=0;bel[top]=tot;}while(top!=x);}
}void rebuild()
{ for(int x=1;x<=n;++x) {for(int i=first[x];i;i=e[i].next) {int to=e[i].to;if(bel[x]==bel[to]) continue;E[++cnt].to=bel[to];E[cnt].next=head[bel[x]];head[bel[x]]=cnt;}W[bel[x]]+=w[x];}
}void spfa()
{dis[bel[st]]=W[bel[st]];q.push(bel[st]);while(!q.empty()) {int x=q.front();q.pop();vis[x]=0;for(int i=head[x];i;i=E[i].next) {int to=E[i].to;if(dis[x]+W[to]>dis[to]) {dis[to]=dis[x]+W[to];if(!vis[to]) {vis[to]=1;q.push(to);}}}}
}int main()
{scanf("%d%d",&n,&m);for(int i=1;i<=m;++i) {int from,to;    scanf("%d%d",&from,&to);add(from,to);}for(int i=1;i<=n;++i) {scanf("%d",&w[i]);if(!dfn[i]) Tarjan(i);}cnt=0;rebuild();scanf("%d%d",&st,&k);spfa();for(int i=1;i<=k;++i) {int x;scanf("%d",&x);ans=max(ans,dis[bel[x]]);}printf("%d",ans);return 0;
}
/*
6 7
1 2
2 3
3 5
2 4
4 1
2 6
6 5
10 12 8 16 1 5
1 4
4 3 5 6
*/