#include <iostream>
#include <algorithm>
#include <cstring>
#include <queue>

using namespace std;
const int maxn = 100005;
vector<int> graph[maxn];
int main()
{
    int n, num_kosta, num_kiril, coins;
    cin >> n >> num_kosta >> num_kiril >> coins;

    vector<bool> visited(n + 1, false);
    queue<int> q;
    for(int i = 0; i < num_kosta; i++) {
        int x;
        cin >> x;
        q.push(x);
        visited[x] = true;
    }

    for(int i = 0; i < num_kiril; i++) {
        int x;
        cin >> x;
        visited[x] = true;
    }

    int res = 0;
    int m;
    cin >> m;
    for(int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    while(!q.empty()) {
        int c = q.front();
        q.pop();

        for(int i = 0; i < (int) graph[c].size(); i++) {
            int neighbour = graph[c][i];
            if(!visited[neighbour] and coins > 0) {
                coins--;
                visited[neighbour] = true;
                q.push(neighbour);
                res++;
            }
        }
    }
    cout << res << endl;

    return 0;
}