CF1771B.Hossam and Friends

Hossam makes a big party, and he will invite his friends to the party.

He has $n$ friends numbered from $1$ to $n$. They will be arranged in a queue as follows: $1, 2, 3, \ldots, n$.

Hossam has a list of $m$ pairs of his friends that don't know each other. Any pair not present in this list are friends.

A subsegment of the queue starting from the friend $a$ and ending at the friend $b$ is $[a, a + 1, a + 2, \ldots, b]$. A subsegment of the queue is called good when all pairs of that segment are friends.

Hossam wants to know how many pairs $(a, b)$ there are ($1 \le a \le b \le n$), such that the subsegment starting from the friend $a$ and ending at the friend $b$ is good.

侯赛姆举办了一场盛大的派对，他将邀请自己的朋友们参加。

他共有 $n$ 位朋友，编号从 $1$ 到 $n$。他们将按如下顺序排成一列：$1, 2, 3, \ldots, n$。

侯赛姆有一份包含 $m$ 对互不认识的朋友的列表。不在该列表中的任意一对朋友彼此都认识。

从朋友 $a$ 开始、到朋友 $b$ 结束的队列子段定义为 $[a, a + 1, a + 2, \ldots, b]$。若该子段中所有朋友对彼此都认识，则称该子段为“好子段”。

侯赛姆想知道，满足 $1 \le a \le b \le n$ 的有序对 $(a, b)$ 共有多少个，使得从朋友 $a$ 开始、到朋友 $b$ 结束的子段是好子段。

The input consists of multiple test cases. The first line contains a single integer $t$ ($1 \le t \le 2 \cdot 10^4$), the number of test cases. Description of the test cases follows.

The first line of each test case contains two integer numbers $n$ and $m$ ($2 \le n \le 10^5$, $0 \le m \le 10^5$) representing the number of friends and the number of pairs, respectively.

The $i$-th of the next $m$ lines contains two integers $x_i$ and $y_i$ ($1 \le x_i, y_i\le n$, $x_i \neq y_i$) representing a pair of Hossam's friends that don't know each other.

Note that pairs can be repeated.

It is guaranteed that the sum of $n$ over all test cases does not exceed $10^5$, and the sum of $m$ over all test cases does not exceed $10^5$.

输入包含多个测试用例。第一行包含一个整数 $t$（$1 \le t \le 2 \cdot 10^4$），表示测试用例的数量。随后是各测试用例的描述。

每个测试用例的第一行包含两个整数 $n$ 和 $m$（$2 \le n \le 10^5$，$0 \le m \le 10^5$），分别表示朋友的数量和互不认识的对数。

接下来的 $m$ 行中，第 $i$ 行包含两个整数 $x_i$ 和 $y_i$（$1 \le x_i, y_i \le n$，$x_i \neq y_i$），表示 Hossam 的一对互不认识的朋友。

注意：这些对可能重复出现。

保证所有测试用例的 $n$ 之和不超过 $10^5$，且所有测试用例的 $m$ 之和不超过 $10^5$。

For each test case print an integer — the number of good subsegments.

对于每个测试用例，输出一个整数——表示“好”子段的数量。

In the first example, the answer is $4$.

The good subsegments are:

[1]

[2]

[3]

[1, 2]

In the second example, the answer is $5$.

The good subsegments are:

[1]

[2]

[3]

[4]

[3, 4]

在第一个例子中，答案是 $4$。

这些好的子段为：

[1]

[2]

[3]

[1, 2]

在第二个例子中，答案是 $5$。

这些好的子段为：

[1]

[2]

[3]

[4]

[3, 4]