#include <bits/stdc++.h>
#define control cout<<"e ne"<<endl;
#define endl '\n'
using namespace std;
int n,m,q,t,y,u[131072],used[131072],x,mx;
vector <int> v[131072];
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
}
void bfs()
{
queue <int> q;
q.push(t);
while(!q.empty())
{
int w=q.front();
q.pop();
for(auto nb:v[w])
{
if(!used[nb])
{
used[nb]=used[w]+1;
q.push(nb);
}
}
}
}
void solve()
{
cin>>n>>m>>q;
for(int i=1;i<=m;i++)
{
int x,y;
cin>>x>>y;
v[y].push_back(x);
}
cin>>t>>y;
for(int i=1;i<=y;i++)
{
cin>>x;
u[x]=1;
}
used[t]=1;
bfs();
mx=-1;
for(int i=1;i<=n;i++)
{
if(!u[i])mx=max(mx,used[i]-1);
}
cout<<mx<<endl;
}
signed main()
{
/*
#ifdef ONLINE_JUDGE
freopen("txt.in","r",stdin)
freopen("txt.out","w",stdout)
#endif
*/
speed();
//int t; cin>>t; while(t--)
solve();
return 0;
}
/*
5 6 3
1 2
2 4
3 4
1 3
3 5
4 5
4 1 1
*/
