#include<bits/stdc++.h>
#define all(vec) vec.begin(),vec.end()
using namespace std;
using ll=long long;
using P=pair<int,int>;
const ll MOD=1000000007LL;
const ll INF=(1<<30);
const ll LINF=(1LL<<60);
template<typename T> void chmax(T &a,T b){a=max(a,b);}
template<typename T> void chmin(T &a,T b){a=min(a,b);}
int main(){
int n,m,qu;cin>>n>>m>>qu;if(qu>1)return 0;
vector<vector<int>> G(n);
for(int i=0;i<m;i++){
int a,b;cin>>a>>b;--a;--b;
G[b].push_back(a);
}
int t,y;cin>>t>>y;--t;
vector<int> x(n);
for(int i=0;i<y;i++){
int c;cin>>c;--c;x[c]=1;
}
priority_queue<P,vector<P>,greater<P>> q;
vector<int> d(n,INF);
q.push(P(0,t));
d[t]=0;
while(!q.empty()){
int v=q.top().second;q.pop();
for(auto e:G[v]){
if(d[e]<=d[v]-1)continue;
d[e]=d[v]-1;
q.push(P(d[e],e));
}
}
int ma=-1;
for(int i=0;i<n;i++){
if(x[i])continue;
if(d[i]==INF)continue;
chmax(ma,-d[i]);
}
cout<<ma<<endl;
}
