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;
  namespace hjt {
  template <typename A, typename B>
  std::ostream &operator<<(std::ostream &o, const std::pair<A, B> &x) {
    return o << '(' << x.first << ',' << x.second << ')';
  }
  }  // namespace hjt
  using namespace hjt;
  const double eps = 1e-7;
  const double PI = acos(-1);
  const int MOD = 998244353;
  const int INF = 0x3f3f3f3f;
  const int N = 2e5 + 7;
  struct Tree {
    struct Node {
      int l, r, v;
    } tr[N << 2];
    void push_up(int i) { tr[i].v = tr[i << 1].v + tr[i << 1 | 1].v; }
    void build(int l, int r, int i = 1) {
      tr[i].l = l;
      tr[i].r = r;
      tr[i].v = 0;
      if (l == r) return tr[i].v = 0, void();
      int mid = (l + r) >> 1;
      build(l, mid, i << 1);
      build(mid + 1, r, i << 1 | 1);
    }
    void add(int x, int k = 1, int i = 1) {
      if (tr[i].l == tr[i].r) return tr[i].v += k, void();
      int mid = (tr[i].l + tr[i].r) >> 1;
      if (x <= mid)
        add(x, k, i << 1);
      else
        add(x, k, i << 1 | 1);
      push_up(i);
    }
    int query(int y, int i = 1) {
      if (tr[i].l == tr[i].r) return tr[i].l;
      int mid = (tr[i].l + tr[i].r) >> 1;
      if (tr[i << 1].v + y > mid) return query(y + tr[i << 1].v, i << 1 | 1);
      return query(y, i << 1);
    }
  };
  struct Combination {
    int fac[N << 1], inv[N << 1];
    Combination() { init(2 * N - 1); }
    void init(const int &n) {
      fac[0] = inv[0] = fac[1] = inv[1] = 1;
      for (int i = 2; i <= n; ++i) {
        fac[i] = 1ll * fac[i - 1] * i % MOD;
        inv[i] = 1ll * (MOD - MOD / i) * inv[MOD % i] % MOD;
      }
      for (int i = 2; i <= n; ++i) {
        inv[i] = 1ll * inv[i] * inv[i - 1] % MOD;
      }
    }
    int A(const int &p, const int &q) {
      return p >= q ? 1ll * fac[p] * inv[p - q] % MOD : 0;
    }
    int C(const int &p, const int &q) {
      return p >= q ? 1ll * fac[p] * inv[q] % MOD * inv[p - q] % MOD : 0;
    }
  };
  int n, m;
  int x[N], y[N], p[N], visp[N];
  Combination comb;
  Tree tree;
  inline void solve() {
    cin >> n >> m;
    for (int i = 1; i <= m; ++i) {
      cin >> x[i] >> y[i];
    }
    int cnt = 0;
    for (int i = m; i; --i) {
      p[x[i]] = tree.query(y[i]);
      tree.add(p[x[i]]);
      visp[p[x[i]]] = 1;
      cnt += visp[p[x[i]] + 1] == 0;
    }
    cout << comb.C(n + n - 1 - cnt, n) << '\n';
    for (int i = 1; i <= m; ++i) {
      tree.add(p[x[i]], -1);
      visp[p[x[i]]] = 0;
    }
  }
  signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int T = 1;
    tree.build(1, N - 1);
    cin >> T;
    for (int t = 1; t <= T; ++t) {
      solve();
    }
    return 0;
  }
  