Buggy python submission (verdict: Time Limit Exceeded):

import operator
class SegmentTree:
    def __init__(self, size, fn=operator.add, default=None, initial_values=None):
        """
        :param int size:
        :param callable fn: 区間に適用する関数。引数を 2 つ取る。min, max, operator.xor など
        :param default:
        :param list initial_values:
        """
        default = default or 0

        # size 以上である最小の 2 冪を size とする
        n = 1
        while n < size:
            n *= 2
        self._size = n
        self._fn = fn

        self._tree = [default] * (self._size * 2 - 1)
        if initial_values:
            i = self._size - 1
            for v in initial_values:
                self._tree[i] = v
                i += 1
            i = self._size - 2
            while i >= 0:
                self._tree[i] = self._fn(self._tree[i * 2 + 1], self._tree[i * 2 + 2])
                i -= 1

    def set(self, i, value):
        """
        i 番目に value を設定
        :param int i:
        :param value:
        :return:
        """
        x = self._size - 1 + i
        self._tree[x] = value

        while x > 0:
            x = (x - 1) // 2
            self._tree[x] = self._fn(self._tree[x * 2 + 1], self._tree[x * 2 + 2])

    def update(self, i, value):
        """
        もとの i 番目と value に fn を適用したものを i 番目に設定
        :param int i:
        :param value:
        :return:
        """
        x = self._size - 1 + i
        self.set(i, self._fn(self._tree[x], value))

    def get(self, from_i, to_i=None, k=0, L=None, r=None):
        """
        [from_i, to_i) に fn を適用した結果を返す
        :param int from_i:
        :param int to_i:
        :param int k: self._tree[k] が、[L, r) に fn を適用した結果を持つ
        :param int L:
        :param int r:
        :return:
        """
        if to_i is None:
            return self._tree[self._size - 1 + from_i]

        L = 0 if L is None else L
        r = self._size if r is None else r

        if from_i <= L and r <= to_i:
            return self._tree[k]

        if to_i <= L or r <= from_i:
            return None

        ret_L = self.get(from_i, to_i, k * 2 + 1, L, (L + r) // 2)
        ret_r = self.get(from_i, to_i, k * 2 + 2, (L + r) // 2, r)
        if ret_L is None:
            return ret_r
        if ret_r is None:
            return ret_L
        return self._fn(ret_L, ret_r)

    def __len__(self):
        return self._size


def resolve():
    N = int(input())
    H = list(map(int, input().split()))
    A = list(map(int, input().split()))

    Flowers = []
    for i in range(N):
        Flowers.append((H[i], (A[i], i)))
    # 高さを昇順にソート
    Flowers.sort()

    seg = SegmentTree(N, fn=max)
    for i in range(N):
        h, (a, idx) = Flowers[i]
        maxV = seg.get(0, idx)
        # l=0, r=0 の時Noneを返す仕様
        if maxV == None:
            maxV = 0
        seg.set(idx, maxV+a)

    ans = seg.get(0, N)
    print(ans)

if __name__ == "__main__":
    resolve()


Fixed submission:
import operator
class SegmentTree:
    def __init__(self, size, fn=operator.add, default=None, initial_values=None):
        """
        :param int size:
        :param callable fn: 区間に適用する関数。引数を 2 つ取る。min, max, operator.xor など
        :param default:
        :param list initial_values:
        """
        default = default or 0
 
        # size 以上である最小の 2 冪を size とする
        n = 1
        while n < size:
            n *= 2
        self._size = n
        self._fn = fn
 
        self._tree = [default] * (self._size * 2 - 1)
        if initial_values:
            i = self._size - 1
            for v in initial_values:
                self._tree[i] = v
                i += 1
            i = self._size - 2
            while i >= 0:
                self._tree[i] = self._fn(self._tree[i * 2 + 1], self._tree[i * 2 + 2])
                i -= 1
 
    def set(self, i, value):
        """
        i 番目に value を設定
        :param int i:
        :param value:
        :return:
        """
        x = self._size - 1 + i
        self._tree[x] = value
 
        while x > 0:
            x = (x - 1) // 2
            self._tree[x] = self._fn(self._tree[x * 2 + 1], self._tree[x * 2 + 2])
 
    def update(self, i, value):
        """
        もとの i 番目と value に fn を適用したものを i 番目に設定
        :param int i:
        :param value:
        :return:
        """
        x = self._size - 1 + i
        self.set(i, self._fn(self._tree[x], value))
 
    def get(self, from_i, to_i=None, k=0, L=None, r=None):
        """
        [from_i, to_i) に fn を適用した結果を返す
        :param int from_i:
        :param int to_i:
        :param int k: self._tree[k] が、[L, r) に fn を適用した結果を持つ
        :param int L:
        :param int r:
        :return:
        """
        if to_i is None:
            return self._tree[self._size - 1 + from_i]
 
        L = 0 if L is None else L
        r = self._size if r is None else r
 
        if from_i <= L and r <= to_i:
            return self._tree[k]
 
        if to_i <= L or r <= from_i:
            return None
 
        ret_L = self.get(from_i, to_i, k * 2 + 1, L, (L + r) // 2)
        ret_r = self.get(from_i, to_i, k * 2 + 2, (L + r) // 2, r)
        if ret_L is None:
            return ret_r
        if ret_r is None:
            return ret_L
        return self._fn(ret_L, ret_r)
 
    def __len__(self):
        return self._size
 
 
def resolve():
    N = int(input())
    H = list(map(int, input().split()))
    A = list(map(int, input().split()))
 
    Flowers = []
    for i in range(N):
        Flowers.append((H[i], (A[i], i)))
    # 高さを昇順にソート
    Flowers.sort()
 
    seg = SegmentTree(N, fn=max)
    for i in range(N):
        h, (a, idx) = Flowers[i]
        maxV = seg.get(0, idx)
        # l=0, r=0 の時Noneを返す仕様
        if maxV == None:
            maxV = 0
        seg.set(idx, maxV+a)
 
    ans = seg.get(0, N)
    print(ans)
    
if __name__ == "__main__":
    resolve()