P2853 [USACO06DEC] Cow Picnic S

#include<bits/stdc++.h>
using namespace std;
int k,n,m,ans,cow[105],pasture[1005],visit[1005];
struct Edge{
	int next;
	int to;
}edge[10005];
int cnt,head[1005];
inline int read()
{
	int x=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9')
	{
		if(ch=='-')
			f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<'9')
	{
		x=(x<<3)+(x<<1)+(ch^48);
		ch=getchar();
	}
	return x*f;
}
void add_Edge(int u,int v)
{
	cnt++;
	edge[cnt].to=v;
	edge[cnt].next=head[u];
	head[u]=cnt;
}
void dfs(int x)
{
	pasture[x]++;
	visit[x]=1;
	for(int i=head[x];i;i=edge[i].next)
		if(!visit[edge[i].to])
			dfs(edge[i].to);
}
int main()
{
	k=read(),n=read(),m=read();
	for(int i=1;i<=k;i++)
		cow[i]=read();
	for(int i=1;i<=m;i++)
	{
		int u=read(),v=read();
		add_Edge(u,v);
	}
	for(int i=1;i<=k;i++)
	{
		memset(visit,0,sizeof(visit));
		visit[cow[i]]=1;
		dfs(cow[i]);
	}
	for(int i=1;i<=n;i++)
		if(pasture[i]==k)
			ans++;
	cout<<ans;
	return 0;
}