B. Shuffletime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputYou 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.InputThe 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).OutputFor 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.ExampleInput
3
6 4 3
1 6
2 3
5 5
4 1 2
2 4
1 2
3 3 2
2 3
1 2
Output
6
2
3
NoteIn the first test case, it is possible to achieve a_k = 1 for every k. To do so, you may use the following operations:  swap a_k and a_4;  swap a_2 and a_2;  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.
3
6 4 3
1 6
2 3
5 5
4 1 2
2 4
1 2
3 3 2
2 3
1 2

6 2 3 
['math', 'two pointers', '*1300']