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>
  constexpr int P = 998244353;
  using i64 = long long;
  int norm(int x) {
    if (x < 0) {
      x += P;
    }
    if (x >= P) {
      x -= P;
    }
    return x;
  }
  template <class T>
  T power(T a, int b) {
    T res = 1;
    for (; b; b /= 2, a *= a) {
      if (b % 2) {
        res *= a;
      }
    }
    return res;
  }
  struct Z {
    int x;
    Z(int x = 0) : x(norm(x)) {}
    int val() const { return x; }
    Z operator-() const { return Z(norm(P - x)); }
    Z inv() const {
      assert(x != 0);
      return power(*this, P - 2);
    }
    Z &operator*=(const Z &rhs) {
      x = i64(x) * rhs.x % P;
      return *this;
    }
    Z &operator+=(const Z &rhs) {
      x = norm(x + rhs.x);
      return *this;
    }
    Z &operator-=(const Z &rhs) {
      x = norm(x - rhs.x);
      return *this;
    }
    Z &operator/=(const Z &rhs) { return *this *= rhs.inv(); }
    friend Z operator*(const Z &lhs, const Z &rhs) {
      Z res = lhs;
      res *= rhs;
      return res;
    }
    friend Z operator+(const Z &lhs, const Z &rhs) {
      Z res = lhs;
      res += rhs;
      return res;
    }
    friend Z operator-(const Z &lhs, const Z &rhs) {
      Z res = lhs;
      res -= rhs;
      return res;
    }
    friend Z operator/(const Z &lhs, const Z &rhs) {
      Z res = lhs;
      res /= rhs;
      return res;
    }
  };
  constexpr int N = 2E5;
  int fen[N];
  void add(int x, int y) {
    for (int i = x + 1; i <= N; i += i & -i) {
      fen[i - 1] += y;
    }
  }
  int find(int k) {
    int x = 0, s = 0;
    for (int i = 1 << 17; i > 0; i >>= 1) {
      if (x + i <= N && x + i - s - fen[x + i - 1] <= k) {
        x += i;
        s += fen[x - 1];
      }
    }
    return x;
  }
  Z fac[2 * N + 1], invfac[2 * N + 1];
  Z binom(int n, int m) { return fac[n] * invfac[m] * invfac[n - m]; }
  void solve() {
    int n, m;
    std::cin >> n >> m;
    int x[m], y[m];
    for (int i = 0; i < m; i++) {
      std::cin >> x[i] >> y[i];
      y[i]--;
    }
    std::set<int> s;
    for (int i = m - 1; i >= 0; i--) {
      s.insert(find(y[i] + 1));
      y[i] = find(y[i]);
      add(y[i], 1);
    }
    for (int i = 0; i < m; i++) {
      add(y[i], -1);
    }
    Z res = binom(n + n - 1 - s.size(), n);
    std::cout << res.val() << "\n";
  }
  int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    fac[0] = 1;
    for (int i = 1; i <= 2 * N; i++) {
      fac[i] = fac[i - 1] * i;
    }
    invfac[2 * N] = fac[2 * N].inv();
    for (int i = 2 * N; i > 0; i--) {
      invfac[i - 1] = invfac[i] * i;
    }
    int t;
    std::cin >> t;
    while (t--) {
      solve();
    }
    return 0;
  }
  