//拓扑排序
#include<bits/stdc++.h>
using namespace std;

int n, k, p, r, ans = -1;
bool flag = false;
int h[5010], e[25000010], ne[25000010], idx = 0, id[5010];
int deg[5010];
struct xyh
{
    int ver;
    int date;
    int cnt;
};
queue<xyh> q;

void add(int a, int b)
{
    e[idx] = b;
    ne[idx] = h[a];
    h[a] = idx;
    idx++;
}

void topsort()
{
    int num = 0;
    for(int i = 0;i < p;i++)
    {
        num++;
        q.push({id[i], 0, num});
    }

  while(!q.empty())
  {
    auto t = q.front();
    q.pop();
    int ver = t.ver, date = t.date, cnt = t.cnt;

    if(ver == k)
    {
        ans = date;
        flag = true;
        return;
    }
    for(int i = h[ver];i != -1;i = ne[i])
    {
        int j = e[i];
        deg[j]--;
        if(deg[j] == 0)
        {
            cnt++;
            q.push({j, date + 1, cnt});
        }
    }
  }
}
int main()
{
    memset(h, -1, sizeof(h));

    cin >> n >> k >> p;
    for(int i = 0;i < p;i++)
    cin >> id[i];

    cin >> r;
    while(r--)
    {
        int v, s;
        cin >> v >> s;
        while(s--)
        {
            int x;
            cin >> x;
            add(x, v);
            deg[v]++;
        }
    }

    topsort();

    cout << ans << endl;


    return 0;
}