CF1324D Pair of Topics

The next lecture in a high school requires two topics to be discussed. The $ i $ -th topic is interesting by $ a_i $ units for the teacher and by $ b_i $ units for the students. The pair of topics $ i $ and $ j $ ( $ i < j $ ) is called good if $ a_i + a_j > b_i + b_j $ (i.e. it is more interesting for the teacher). Your task is to find the number of good pairs of topics.

The first line of the input contains one integer $ n $ ( $ 2 \le n \le 2 \cdot 10^5 $ ) — the number of topics. The second line of the input contains $ n $ integers $ a_1, a_2, \dots, a_n $ ( $ 1 \le a_i \le 10^9 $ ), where $ a_i $ is the interestingness of the $ i $ -th topic for the teacher. The third line of the input contains $ n $ integers $ b_1, b_2, \dots, b_n $ ( $ 1 \le b_i \le 10^9 $ ), where $ b_i $ is the interestingness of the $ i $ -th topic for the students.

Print one integer — the number of good pairs of topic.