Buggy python submission (verdict: Runtime Error):
def conKey(i, j, k):
    return str(i)+'-'+str(j)+'-'+str(k)


def getKey(s):
    return map(int, s.split('-'))


import heapq
X, Y, Z, K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C = list(map(int, input().split()))
A.sort(reverse=True)
B.sort(reverse=True)
C.sort(reverse=True)

h = []
stack = set([])
ans = []
i, j, k = 0, 0, 0
heapq.heappush(h, (-(A[i]+B[j]+C[k]), conKey(i, j, k)))
stack.add(conKey(i, j, k))
for _ in range(K):
    tmp, key = heapq.heappop(h)
    print(-tmp)
    i, j, k = getKey(key)
    key_0 = [i, j, k]

    for m in range(3):
        key_tmp = key_0.copy()
        key_tmp[m] += 1
        tmp_sum = A[key_tmp[0]] + B[key_tmp[1]] + C[key_tmp[2]]

        str_key = conKey(*key_tmp)
        if str_key not in stack:
            heapq.heappush(h, (-tmp_sum, str_key))
            stack.add(str_key)

Fixed submission:

X, Y, Z, K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C = list(map(int, input().split()))
A.sort(reverse=True)
B.sort(reverse=True)
C.sort(reverse=True)

# まずA, Bで総当たり、上位K個をスタック
tmp = [a+b for a in A for b in B]
tmp.sort(reverse=True)
tmp = tmp[:K]

# 残りのc個に対しても総当たり
ans = [t+c for t in tmp for c in C]
ans.sort(reverse=True)
ans = ans[:K]
for s in ans:
    print(s)

Buggy python submission (verdict: Time Limit Exceeded):
X, Y, Z, K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C = list(map(int, input().split()))

# まずA, Bで総当たり、上位K個をスタック
tmp = [a+b for a in A for b in B]
tmp.sort(reverse=True)
tmp = tmp[:K]

# 残りのc個に対しても総当たり
ans = [t+c for t in tmp for c in C]
ans.sort(reverse=True)
ans = ans[:K]

for s in ans:
    print(s)

Fixed submission:

X, Y, Z, K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C = list(map(int, input().split()))
A.sort(reverse=True)
B.sort(reverse=True)
C.sort(reverse=True)

# まずA, Bで総当たり、上位K個をスタック
tmp = [a+b for a in A for b in B]
tmp.sort(reverse=True)
tmp = tmp[:K]

# 残りのc個に対しても総当たり
ans = [t+c for t in tmp for c in C]
ans.sort(reverse=True)
ans = ans[:K]
for s in ans:
    print(s)

Buggy python submission (verdict: Time Limit Exceeded):
X, Y, Z, K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C = list(map(int, input().split()))
A.sort(reverse=True)
B.sort(reverse=True)
C.sort(reverse=True)

# まずA, Bで総当たり、上位K個をスタック
tmp = []
for a in A:
    for b in B:
        tmp.append(a+b)
tmp = sorted(tmp, reverse=True)[:K]
# 残りのc個に対しても総当たり
ans = []
for s in tmp:
    for c in C:
        ans.append(s+c)
ans = sorted(ans, reverse=True)[:K]
for s in ans:
    print(s)


Fixed submission:

X, Y, Z, K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C = list(map(int, input().split()))
A.sort(reverse=True)
B.sort(reverse=True)
C.sort(reverse=True)

# まずA, Bで総当たり、上位K個をスタック
tmp = [a+b for a in A for b in B]
tmp.sort(reverse=True)
tmp = tmp[:K]

# 残りのc個に対しても総当たり
ans = [t+c for t in tmp for c in C]
ans.sort(reverse=True)
ans = ans[:K]
for s in ans:
    print(s)