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import sys
from collections import deque
def main():
    n, m, k, r = map(int, sys.stdin.readline().split())
    nodes = []
    for _ in range(n):
        x, y = map(int, sys.stdin.readline().split())
        nodes.append((x, y))
    new_nodes = []
    for _ in range(m):
        x, y = map(int, sys.stdin.readline().split())
        new_nodes.append((x, y))
    
    # Encode all nodes
    all_nodes = nodes + new_nodes
    node_pos = [ (x,y) for (x,y) in all_nodes ]
    node_id = [i for i in range(len(all_nodes))]
    target_pos = node_pos[1]  # node 1 is the second router
    # Create adjacency list
    adj = [[] for _ in range(len(all_nodes))]
    for i in range(len(all_nodes)):
        for j in range(i+1, len(all_nodes)):
            x1, y1 = node_pos[i]
                x2, y2 = node_pos[j]
                dx = x1 - x2
                dy = y1 - y2
                dist = dx*dx + dy*dy
                if dist <= r*r:
                    adj[i].append(j)
                    adj[j].append(i)
    
    # BFS setup
    INF = float('inf')
    distance = [ [INF]*(k+1) for _ in range(len(all_nodes)) ]
    start_pos = node_id[0]  # position of first router
    distance[start_pos][0] = 0
    queue = deque()
    queue.append( (start_pos, 0) )
    found = False
    min_trans = INF
    while queue:
        pos, added = queue.popleft()
        if pos == node_id[1]:  # reached the second router
            if added <=k:
                if distance[pos][added] < min_trans:
                    min_trans = distance[pos][added]
                    found = True
            continue
        if distance[pos][added] >= INF:
            continue
        for neighbor in adj[pos]:
            if neighbor < n:  # original node
                new_added = added
            else:  # new node
                if added >= k:
                    continue
                new_added = added + 1
            new_dist = distance[pos][added] + 1
            if new_dist < distance[neighbor][new_added]:
                distance[neighbor][new_added] = new_dist
                queue.append( (neighbor, new_added) )
    
    print(min_trans if found else -1)
if __name__ == "__main__":
    main()

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