Buggy python submission (verdict: Time Limit Exceeded):
import sys
import heapq

input = sys.stdin.readline


def main():
    X, Y, Z, K = map(int, input().split())
    A = list(map(lambda x: -int(x), input().split()))
    B = list(map(lambda x: -int(x), input().split()))
    C = list(map(lambda x: -int(x), input().split()))

    A.sort()
    B.sort()
    C.sort()

    p_queue = [(A[0] + B[0] + C[0], 0, 0, 0)]
    appear = [[[False for _ in range(Z)] for _ in range(Y)] for _ in range(X)]
    appear[0][0][0] = True
    ans = []
    while len(ans) < K:
        s, i_A, i_B, i_C = heapq.heappop(p_queue)
        ans.append(-s)
        if i_A < X - 1 and not appear[i_A + 1][i_B][i_C]:
            appear[i_A + 1][i_B][i_C] = True
            t = s - A[i_A] + A[i_A + 1]
            heapq.heappush(p_queue, (t, i_A + 1, i_B, i_C))
        if i_B < Y - 1 and not appear[i_A][i_B + 1][i_C]:
            appear[i_A][i_B + 1][i_C] = True
            t = s - B[i_B] + B[i_B + 1]
            heapq.heappush(p_queue, (t, i_A, i_B + 1, i_C))
        if i_C < Z - 1 and not appear[i_A][i_B][i_C + 1]:
            appear[i_A][i_B][i_C + 1] = True
            t = s - C[i_C] + C[i_C + 1]
            heapq.heappush(p_queue, (t, i_A, i_B, i_C + 1))

    print("\n".join(map(str, ans)))


if __name__ == "__main__":
    main()


Fixed submission:
import sys
import heapq

input = sys.stdin.readline


def main():
    X, Y, Z, K = map(int, input().split())
    A = list(map(lambda x: -int(x), input().split()))
    B = list(map(lambda x: -int(x), input().split()))
    C = list(map(lambda x: -int(x), input().split()))

    A.sort()
    B.sort()
    C.sort()

    p_queue = [(A[0] + B[0] + C[0], 0, 0, 0)]
    visited = set()
    visited.add((0, 0, 0))
    ans = []
    while len(ans) < K:
        s, i_A, i_B, i_C = heapq.heappop(p_queue)
        ans.append(-s)
        if i_A < X - 1 and (i_A + 1, i_B, i_C) not in visited:
            visited.add((i_A + 1, i_B, i_C))
            t = s - A[i_A] + A[i_A + 1]
            heapq.heappush(p_queue, (t, i_A + 1, i_B, i_C))
        if i_B < Y - 1 and (i_A, i_B + 1, i_C) not in visited:
            visited.add((i_A, i_B + 1, i_C))
            t = s - B[i_B] + B[i_B + 1]
            heapq.heappush(p_queue, (t, i_A, i_B + 1, i_C))
        if i_C < Z - 1 and (i_A, i_B, i_C + 1) not in visited:
            visited.add((i_A, i_B, i_C + 1))
            t = s - C[i_C] + C[i_C + 1]
            heapq.heappush(p_queue, (t, i_A, i_B, i_C + 1))

    print("\n".join(map(str, ans)))


if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
import heapq

input = sys.stdin.readline


def main():
    X, Y, Z, K = map(int, input().split())
    A = list(map(lambda x: -int(x), input().split()))
    B = list(map(lambda x: -int(x), input().split()))
    C = list(map(lambda x: -int(x), input().split()))

    A.sort()
    B.sort()
    C.sort()

    p_queue = [(A[0] + B[0] + C[0], 0, 0, 0)]
    appear = [[[False for _ in range(Z)] for _ in range(Y)] for _ in range(X)]
    appear[0][0][0] = True
    ans = []
    while len(ans) < K:
        s, i_A, i_B, i_C = heapq.heappop(p_queue)
        ans.append(-s)
        if i_A < X - 1 and not appear[i_A + 1][i_B][i_C]:
            appear[i_A + 1][i_B][i_C] = True
            t = s - A[i_A] + A[i_A + 1]
            p_queue.append((t, i_A + 1, i_B, i_C))
        if i_B < Y - 1 and not appear[i_A][i_B + 1][i_C]:
            appear[i_A][i_B + 1][i_C] = True
            t = s - B[i_B] + B[i_B + 1]
            p_queue.append((t, i_A, i_B + 1, i_C))
        if i_C < Z - 1 and not appear[i_A][i_B][i_C + 1]:
            appear[i_A][i_B][i_C + 1] = True
            t = s - C[i_C] + C[i_C + 1]
            p_queue.append((t, i_A, i_B, i_C + 1))

        heapq.heapify(p_queue)

    print("\n".join(map(str, ans)))


if __name__ == "__main__":
    main()


Fixed submission:
import sys
import heapq

input = sys.stdin.readline


def main():
    X, Y, Z, K = map(int, input().split())
    A = list(map(lambda x: -int(x), input().split()))
    B = list(map(lambda x: -int(x), input().split()))
    C = list(map(lambda x: -int(x), input().split()))

    A.sort()
    B.sort()
    C.sort()

    p_queue = [(A[0] + B[0] + C[0], 0, 0, 0)]
    visited = set()
    visited.add((0, 0, 0))
    ans = []
    while len(ans) < K:
        s, i_A, i_B, i_C = heapq.heappop(p_queue)
        ans.append(-s)
        if i_A < X - 1 and (i_A + 1, i_B, i_C) not in visited:
            visited.add((i_A + 1, i_B, i_C))
            t = s - A[i_A] + A[i_A + 1]
            heapq.heappush(p_queue, (t, i_A + 1, i_B, i_C))
        if i_B < Y - 1 and (i_A, i_B + 1, i_C) not in visited:
            visited.add((i_A, i_B + 1, i_C))
            t = s - B[i_B] + B[i_B + 1]
            heapq.heappush(p_queue, (t, i_A, i_B + 1, i_C))
        if i_C < Z - 1 and (i_A, i_B, i_C + 1) not in visited:
            visited.add((i_A, i_B, i_C + 1))
            t = s - C[i_C] + C[i_C + 1]
            heapq.heappush(p_queue, (t, i_A, i_B, i_C + 1))

    print("\n".join(map(str, ans)))


if __name__ == "__main__":
    main()