#include <iostream>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;

const int N = 210;
typedef long long ll;
typedef pair<int, int> PII;
vector<int> qs[N];
PII vinfoS[N];
ll n, m, k, r;
int d[N][N];

bool check(int i, int j) {
    ll dx = vinfoS[i].first - vinfoS[j].first;
    ll dy = vinfoS[i].second - vinfoS[j].second;
    if (dx * dx + dy * dy <= r * r) {
        return true;
    }
    else {
        return false;
    }
}
int main() {
    cin >> n >> m >> k >> r;
    for (int i = 0; i < n + m; i ++) {
        cin >> vinfoS[i].first >> vinfoS[i].second;
    }

    for (int i = 1; i < n + m; i++) {
        for (int j = 0; j < i; j++) {
            if (check(i, j)) {
                qs[i].push_back(j);
                qs[j].push_back(i);
            }
        }
    }
    queue<int> q;
    q.push(0);
    memset(d, 0x3f, sizeof d);
    d[0][0] = 0;
    while (q.size()) {
        int out = q.front();
        q.pop();
        for (auto x : qs[out]) {
            if (x >= n) {
                for (int j = 0; j < k; j ++) {
                    if (d[x][j + 1] > d[out][j] + 1) {
                        d[x][j + 1] = d[out][j] + 1;
                        q.push(x);
                    }
                }
            }
            else {
                for (int j = 0; j <= k; j ++) {
                    if (d[x][j] > d[out][j] + 1) {
                        d[x][j] = d[out][j] + 1;
                        q.push(x);
                    }
                }
            }
        }
    }
    int ans = m + n;
    for (int i = 0; i <= k; i++) {
        if (ans > d[1][i]) {
            ans = d[1][i];
        }
    }
    cout << ans - 1 << endl;
    return 0;
}