Buggy python submission (verdict: Time Limit Exceeded):
import sys
from operator import itemgetter
input = sys.stdin.readline

_n, _k = map(int, input().split())
_a = input()[:-1]
_f = input()[:-1]
alist = [item for item in map(int, _a.split())]
flist = [item for item in map(int, _f.split())]


def chker(costs, diffs, max_k):
    if sum(costs) <= max_k:
        print(0)
        return

    costs.sort()
    diffs.sort(reverse=True)
    sclist = sorted([[item1, item2, item1 * item2] for item1, item2 in zip(costs, diffs)], key=itemgetter(2), reverse=True)
    for k in range(max_k, 0, -1):
        sclist[0][0] = sclist[0][0] - 1
        if sclist[0][0] == 0:
            sclist = sclist[1:]
        else:
            sclist[0][2] = sclist[0][0] * sclist[0][1]
            sclist.sort(key=itemgetter(2), reverse=True)

    print(sclist[0][2])


chker(alist, flist, _k)


Fixed submission:
import numpy as np
import sys
input = sys.stdin.readline

_n, _k = map(int, input().split())
alist = [int(item) for item in input().split()]
flist = [int(item) for item in input().split()]


def chker(costs, diffs, max_k):
	costs = np.sort(costs)[::-1]
	diffs = np.sort(diffs)
	
	_min, _max = 0, 10 ** 12
	while _min < _max:
		_mid = (_min + _max) // 2
		cnt = costs - _mid // diffs
		if cnt[cnt > 0].sum() <= max_k:
			_max = _mid
		else:
			_min = _mid + 1


	print(_min)


chker(alist, flist, _k)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

_n, _k = map(int, input().split())
_a = input()[:-1]
_f = input()[:-1]
alist = [item for item in map(int, _a.split())]
flist = [item for item in map(int, _f.split())]


def chker(costs, diffs, max_k):
    if sum(costs) <= max_k:
        print(0)
        return

    costs.sort()
    diffs.sort(reverse=True)
    sclist = sorted([[item1, item2, item1 * item2] for item1, item2 in zip(costs, diffs)], key=lambda x:x[2], reverse=True)
    k = max_k
    while k > 0:
        sclist[0][0] = sclist[0][0] - 1
        if sclist[0][0] == 0:
            sclist = sclist[1:]
        else:
            sclist[0][2] = sclist[0][0] * sclist[0][1]
            sclist.sort(key=lambda x:x[2], reverse=True)

        k -= 1

    print(sclist[0][2])


chker(alist, flist, _k)


Fixed submission:
import numpy as np
import sys
input = sys.stdin.readline

_n, _k = map(int, input().split())
alist = [int(item) for item in input().split()]
flist = [int(item) for item in input().split()]


def chker(costs, diffs, max_k):
	costs = np.sort(costs)[::-1]
	diffs = np.sort(diffs)
	
	_min, _max = 0, 10 ** 12
	while _min < _max:
		_mid = (_min + _max) // 2
		cnt = costs - _mid // diffs
		if cnt[cnt > 0].sum() <= max_k:
			_max = _mid
		else:
			_min = _mid + 1


	print(_min)


chker(alist, flist, _k)

Buggy python submission (verdict: Runtime Error):
import sys
import math
input = sys.stdin.readline

_n, _k = map(int, input().split())
_a = input()[:-1]
_f = input()[:-1]
alist = [item for item in _a]
flist = [item for item in _f]


def chker(costs, diffs, max_k):
    if sum(costs) <= max_k:
        print(0)

    costs.sort()
    diffs.sort(reverse=True)
    sclist = [(item1, item2, item1 * item2) for item1, item2 in zip(costs, diffs)].sort(key=lambda x:x[2], reverse=True)
    k = max_k
    while k > 0:
        k -= 1
        sclist[0][0] = sclist[0][0] - 1
        if sclist[0][0] == 0:
            sclist = sclist[1:]
        else:
            sclist[0][2] = sclist[0][0] * sclist[0][1]
            sclist.sort(key=lambda x:x[2], reverse=True)

    print(sclist[0][2])


chker(alist, flist, _k)


Fixed submission:
import numpy as np
import sys
input = sys.stdin.readline

_n, _k = map(int, input().split())
alist = [int(item) for item in input().split()]
flist = [int(item) for item in input().split()]


def chker(costs, diffs, max_k):
	costs = np.sort(costs)[::-1]
	diffs = np.sort(diffs)
	
	_min, _max = 0, 10 ** 12
	while _min < _max:
		_mid = (_min + _max) // 2
		cnt = costs - _mid // diffs
		if cnt[cnt > 0].sum() <= max_k:
			_max = _mid
		else:
			_min = _mid + 1


	print(_min)


chker(alist, flist, _k)