#include <iostream>
#include <cstring>
#include <vector>
#include <cmath>
#include <queue>
using namespace std;
const int maxn = 1e5 + 10;
vector<int> graph[maxn];

int main() {
    ios_base::sync_with_stdio(false);
    int n, B1, B2, P;
    cin >> n >> B1 >> B2 >> P;

    vector<int> kosta(B1), kiril(B2);

    queue<int> q;

    vector<bool> visited(n + 1, false);
    for(int i = 0; i < B1; i++) {
        cin >> kosta[i];
        q.push(kosta[i]);

        visited[kosta[i]] = true;
    }

    for(int i = 0; i < B2; i++) {
        cin >> kiril[i];
        visited[kiril[i]] = true;
    }

    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);
    }

    int res = 0;
    while(!q.empty()) {
        int node = q.front();
        q.pop();

        for(int i = 0; i < (int) graph[node].size(); i++) {
            int neighbour = graph[node][i];

            if(!visited[neighbour]) {
                q.push(neighbour);
                visited[neighbour] = true;

                if(res + 1 <= P) {
                    res++;
                }
            }
        }
    }

    cout << res << endl;
    return 0;
}