题目描述
There are $n$ people on the number line; the $i$-th person is at point $a_i$ and wants to go to point $b_i$. For each person, $a_i < b_i$, and the starting and ending points of all people are distinct. (That is, all of the $2n$ numbers $a_1, a_2, \dots, a_n, b_1, b_2, \dots, b_n$ are distinct.)
All the people will start moving simultaneously at a speed of $1$ unit per second until they reach their final point $b_i$. When two people meet at the same point, they will greet each other once. How many greetings will there be?
Note that a person can still greet other people even if they have reached their final point.
Input
The first line of the input contains a single integer $t$ ($1 \le t \le 10^4$) — the number of test cases. The description of test cases follows.
The first line of each test case contains a single integer $n$ ($1 \le n \le 2 \cdot 10^5$) — the number of people.
Then $n$ lines follow, the $i$-th of which contains two integers $a_i$ and $b_i$ ($-10^9 \leq a_i < b_i \leq 10^9$) — the starting and ending positions of each person.
For each test case, all of the $2n$ numbers $a_1, a_2, \dots, a_n, b_1, b_2, \dots, b_n$ are distinct.
The sum of $n$ over all test cases does not exceed $2 \cdot 10^5$.
Output
For each test case, output a single integer denoting the number of greetings that will happen.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
样例输出
提示
In the first test case, the two people will meet at point $3$ and greet each other.