Buggy python submission (verdict: Time Limit Exceeded):
#coding:utf-8
import sys
import bisect
import math
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = lambda *something : print(*something) if DEBUG else 0
DEBUG = True
def main(given = sys.stdin.readline):
    input = lambda : given().rstrip()
    LMIIS = lambda : list(map(int,input().split()))
    II = lambda : int(input())
    XLMIIS = lambda x : [LMIIS() for _ in range(x)]

    n, k = LMIIS()
    aa = LMIIS()
    ff = LMIIS()
    aa.sort(reverse=True)
    ff.sort()
    a = tuple(aa)
    f = tuple(ff)


    max_ = 10**12
    min_ = 0

    while max_ != min_ + 1:
        x = (max_ + min_) // 2
        shugyo = 0
        for i in range(n):
            shugyo += max(0, a[i] - x // f[i])

        if shugyo <= k:
            max_ = x
        else:
            min_ = x


    if x == min_:
        x += 1
    if sum(a) <= k:
        x = 0
    print(x)

if __name__ == '__main__':
    main()


Fixed submission:
#coding:utf-8
import sys
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = lambda *something : print(*something) if DEBUG else 0
DEBUG = True
def main(given = sys.stdin.readline):
    input = lambda : given().rstrip()
    LMIIS = lambda : list(map(int,input().split()))
    II = lambda : int(input())
    XLMIIS = lambda x : [LMIIS() for _ in range(x)]

    n, k = LMIIS()
    aa = LMIIS()
    ff = LMIIS()
    aa.sort(reverse=True)
    ff.sort()
    a = tuple(aa)
    f = tuple(ff)


    max_ = 10**12
    min_ = 0

    while max_ != min_ + 1:
        x = (max_ + min_) // 2
        shugyo = 0
        for i in range(n):
            shugyo += max(0, a[i] - x // f[i])

        if shugyo <= k:
            max_ = x
        else:
            min_ = x


    if x == min_:
        x += 1
    if sum(a) <= k:
        x = 0
    print(x)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
#coding:utf-8
import sys
import bisect
import math
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = lambda *something : print(*something) if DEBUG else 0
DEBUG = True
def main(given = sys.stdin.readline):
    input = lambda : given().rstrip()
    LMIIS = lambda : list(map(int,input().split()))
    II = lambda : int(input())
    XLMIIS = lambda x : [LMIIS() for _ in range(x)]

    n, k = LMIIS()
    a = LMIIS()
    f = LMIIS()
    a.sort(reverse=True)
    f.sort()


    max_ = 10**12
    min_ = 0

    while True:
        x = (max_ + min_) // 2
        shugyo = 0
        for i in range(n):
            shugyo += max(0, a[i] - x // f[i])

        if shugyo <= k:
            max_ = x
        else:
            min_ = x


        if max_ == min_ + 1:
            if x == min_:
                x += 1
            if sum(a) <= k:
                x = 0
            break
    print(x)

if __name__ == '__main__':
    main()


Fixed submission:
#coding:utf-8
import sys
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = lambda *something : print(*something) if DEBUG else 0
DEBUG = True
def main(given = sys.stdin.readline):
    input = lambda : given().rstrip()
    LMIIS = lambda : list(map(int,input().split()))
    II = lambda : int(input())
    XLMIIS = lambda x : [LMIIS() for _ in range(x)]

    n, k = LMIIS()
    aa = LMIIS()
    ff = LMIIS()
    aa.sort(reverse=True)
    ff.sort()
    a = tuple(aa)
    f = tuple(ff)


    max_ = 10**12
    min_ = 0

    while max_ != min_ + 1:
        x = (max_ + min_) // 2
        shugyo = 0
        for i in range(n):
            shugyo += max(0, a[i] - x // f[i])

        if shugyo <= k:
            max_ = x
        else:
            min_ = x


    if x == min_:
        x += 1
    if sum(a) <= k:
        x = 0
    print(x)

if __name__ == '__main__':
    main()