Solve the programming task below in a Python markdown code block.
Read problems statements in [Hindi], [Mandarin Chinese], [Russian], [Vietnamese], and [Bengali] as well.

Chef lives in a huge apartment building with $N$ floors, numbered $0$ (ground floor) through $N$ (terrace). Unfortunately, it has only one lift. We say that when the lift travels from a floor $a$ to a floor $b$, it travels $|b-a|$ floors.

Initially, the lift is on the ground floor. Then, it receives $Q$ requests (numbered $1$ through $Q$). For each valid $i$, the $i$-th request is for the lift to move from its current floor to a source floor $f_{i}$, where some people enter the lift, and then move to a destination floor $d_{i}$, where they exit the lift. The lift should not stop anywhere in between moving to the floor $f_{i}$ or from the floor $f_{i}$ to the floor $d_{i}$. The lift must serve the requests sequentially, i.e. completely fulfill request $1$, then request $2$ and so on. The lift does not move anywhere after serving the final request.

Find the total number of floors the lift needs to travel to fulfill all the requests.

------  Input ------
The first line of the input contains a single integer $T$ denoting the number of test cases. The description of $T$ test cases follows.
The first line of each test case contains two space-separated integers $N$ and $Q$.
The following $Q$ lines describe requests. For each valid $i$, the $i$-th of these lines contains two space-separated integers $f_{i}$ and $d_{i}$.

------  Output ------
For each test case, print a single line containing one integer ― the total number of floors travelled by the lift.

------  Constraints ------
$1 ≤ T ≤ 250$
$1 ≤ N ≤ 10^{6}$
$1 ≤ Q ≤ 10^{5}$
$0 ≤ f_{i}, d_{i} ≤ N$ for each valid $i$
$f_{i} \neq d_{i}$ for each valid $i$
the sum of $Q$ over all test cases does not exceed $10^{5}$

----- Sample Input 1 ------ 
1

2 3

1 2

0 1

1 0
----- Sample Output 1 ------ 
6
----- explanation 1 ------ 
Example case 1: The lift travels $2$ floors up to serve the first request, $3$ floors ($2$ down, then $1$ up) to serve the second request and $1$ floor down to serve the third request. Note that in this case, the lift returned to the ground floor, but it may end up at any floor.