B"Consider the insertion sort algorithm used to sort an integer sequence [a_1, a_2, ldots, a_n] of length n in non-decreasing order. For each i in order from 2 to n , do the following. If a_i ge a_{i-1} , do nothing and move on to the next value of i . Otherwise, find the smallest j such that a_i < a_j , shift the elements on positions from j to i-1 by one position to the right, and write down the initial value of a_i to position j . In this case we'll say that we performed an insertion of an element from position i to position j . It can be noticed that after processing any i , the prefix of the sequence [a_1, a_2, ldots, a_i] is sorted in non-decreasing order, therefore, the algorithm indeed sorts any sequence. For example, sorting [4, 5, 3, 1, 3] proceeds as follows: You are given an integer n and a list of m integer pairs (x_i, y_i) . We are interested in sequences such that if you sort them using the above algorithm, exactly m insertions will be performed: first from position x_1 to position y_1 , then from position x_2 to position y_2 , ..., finally, from position x_m to position y_m . How many sequences of length n consisting of (not necessarily distinct) integers between 1 and n , inclusive, satisfy the above condition? Print this number modulo 998 ,244 ,353 . Each test contains multiple test cases. The first line contains the number of test cases t ( 1 <= t <= 10^5 ). Description of the test cases follows. The first line of each test case contains two integers n and m ( 2 <= n <= 2 cdot 10^5 ; 0 <= m < n ) -- the length of the sequence and the number of insertions. The i -th of the following m lines contains two integers x_i and y_i ( 2 <= x_1 < x_2 < ldots < x_m <= n ; 1 <= y_i < x_i ). These li"...