CF1366B.Shuffle

You are given an array consisting of $n$ integers $a_1$ , $a_2$ , ..., $a_n$ . Initially $a_x = 1$ , all other elements are equal to $0$ .

You have to perform $m$ operations. During the $i$ -th operation, you choose two indices $c$ and $d$ such that $l_i \le c, d \le r_i$ , and swap $a_c$ and $a_d$ .

Calculate the number of indices $k$ such that it is possible to choose the operations so that $a_k = 1$ in the end.

The first line contains a single integer $t$ ( $1 \le t \le 100$ ) — the number of test cases. Then the description of $t$ testcases follow.

The first line of each test case contains three integers $n$ , $x$ and $m$ ( $1 \le n \le 10^9$ ; $1 \le m \le 100$ ; $1 \le x \le n$ ).

Each of next $m$ lines contains the descriptions of the operations; the $i$ -th line contains two integers $l_i$ and $r_i$ ( $1 \le l_i \le r_i \le n$ ).

For each test case print one integer — the number of indices $k$ such that it is possible to choose the operations so that $a_k = 1$ in the end.

In the first test case, it is possible to achieve $a_k = 1$ for every $k$ . To do so, you may use the following operations:

1. swap $a_k$ and $a_4$ ;
2. swap $a_2$ and $a_2$ ;
3. swap $a_5$ and $a_5$ .

In the second test case, only $k = 1$ and $k = 2$ are possible answers. To achieve $a_1 = 1$ , you have to swap $a_1$ and $a_1$ during the second operation. To achieve $a_2 = 1$ , you have to swap $a_1$ and $a_2$ during the second operation.