description: Consider the insertion sort algorithm used to sort an integer sequence [a_1, a_2, …, a_n] of length n in non-decreasing order.
  
  For each i in order from 2 to n, do the following. If a_i ≥ 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, …, 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: 
  
    * i = 2: a_2 ≥ a_1, do nothing; 
    * i = 3: j = 1, insert from position 3 to position 1: [3, 4, 5, 1, 3]; 
    * i = 4: j = 1, insert from position 4 to position 1: [1, 3, 4, 5, 3]; 
    * i = 5: j = 3, insert from position 5 to position 3: [1, 3, 3, 4, 5]. 
  
  
  
  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.
  
  Input
  
  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 ⋅ 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 < … < x_m ≤ n; 1 ≤ y_i < x_i). These lines describe the sequence of insertions in chronological order.
  
  It is guaranteed that the sum of m over all test cases does not exceed 2 ⋅ 10^5. Note that there is no constraint on the sum of n of the same kind.
  
  Output
  
  For each test case, print the number of sequences of length n consisting of integers from 1 to n such that sorting them with the described algorithm produces the given sequence of insertions, modulo 998 244 353.
  
  Example
  
  Input
  
  
  3
  3 0
  3 2
  2 1
  3 1
  5 3
  3 1
  4 1
  5 3
  
  
  Output
  
  
  10
  1
  21
  
  Note
  
  In the first test case, the algorithm performs no insertions — therefore, the initial sequence is already sorted in non-decreasing order. There are 10 such sequences: [1, 1, 1], [1, 1, 2], [1, 1, 3], [1, 2, 2], [1, 2, 3], [1, 3, 3], [2, 2, 2], [2, 2, 3], [2, 3, 3], [3, 3, 3].
  
  In the second test case, the only sequence satisfying the conditions is [3, 2, 1].
  
  In the third test case, [4, 5, 3, 1, 3] is one of the sought sequences.
solution: #include <bits/stdc++.h>
  using namespace std;
  struct Q {
    vector<int> c;
    vector<int> buf;
    Q(int n) {
      c = vector<int>(n + 1);
      for (int i = 1; i <= n; i++) {
        c[i] = lowbit(i);
      }
    }
    int lowbit(int x) { return x & -x; }
    void update(int p) {
      for (int i = p; i < c.size(); i += lowbit(i)) {
        c[i]--;
        buf.push_back(i);
      }
    }
    void rollback() {
      for (auto &p : buf) {
        c[p]++;
      }
      buf.clear();
    }
    int find(int sum) {
      int temp = 0;
      int p = 0;
      for (int i = 20; i >= 0; i--) {
        if (p + (1 << i) < c.size() && temp + c[p + (1 << i)] < sum) {
          p += 1 << i;
          temp += c[p];
        }
      }
      return p + 1;
    }
  } q(2e5);
  vector<int64_t> fac(4e5 + 1), ifac(4e5 + 1);
  const int mod = 998244353;
  int powermod(int64_t a, int n, int mod) {
    int64_t ans = 1;
    while (n) {
      if (n & 1) {
        ans = ans * a % mod;
      }
      a = a * a % mod;
      n >>= 1;
    }
    return ans;
  }
  int comb(int n, int m) { return fac[n] * ifac[n - m] % mod * ifac[m] % mod; }
  void solve() {
    int n, m;
    cin >> n >> m;
    vector<pair<int, int>> ins(m);
    for (auto &[x, y] : ins) {
      cin >> x >> y;
    }
    unordered_set<int> flag;
    int c = 0;
    for (int i = m - 1; i >= 0; i--) {
      auto [x, y] = ins[i];
      int p = q.find(y);
      q.update(p);
      c += !flag.count(p + 1);
      flag.insert(p);
    }
    q.rollback();
    cout << comb(n + (n - 1 - c), n) << endl;
  }
  int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t = 1;
    cin >> t;
    fac[0] = ifac[0] = 1;
    for (int i = 1; i < fac.size(); i++) {
      fac[i] = fac[i - 1] * i % mod;
      ifac[i] = powermod(fac[i], mod - 2, mod) % mod;
    }
    while (t--) {
      solve();
    }
    return 0;
  }
  