#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#define debug(...) fprintf(stderr, ##__VA_ARGS__)
#else
#define endl "\n"
#define debug(...) void(0)
#endif
using LL = long long;
template <unsigned umod>
struct modint {/*{{{*/
  static constexpr int mod = umod;
  unsigned v;
  modint() = default;
  template <class T, enable_if_t<is_integral<T>::value, int> = 0>
    modint(const T& y) : v((unsigned)(y % mod + (is_signed<T>() && y < 0 ? mod : 0))) {}
  modint& operator+=(const modint& rhs) { v += rhs.v; if (v >= umod) v -= umod; return *this; }
  modint& operator-=(const modint& rhs) { v -= rhs.v; if (v >= umod) v += umod; return *this; }
  modint& operator*=(const modint& rhs) { v = (unsigned)(1ull * v * rhs.v % umod); return *this; }
  modint& operator/=(const modint& rhs) { assert(rhs.v); return *this *= qpow(rhs, mod - 2); }
  friend modint operator+(modint lhs, const modint& rhs) { return lhs += rhs; }
  friend modint operator-(modint lhs, const modint& rhs) { return lhs -= rhs; }
  friend modint operator*(modint lhs, const modint& rhs) { return lhs *= rhs; }
  friend modint operator/(modint lhs, const modint& rhs) { return lhs /= rhs; }
  template <class T> friend modint qpow(modint a, T b) {
    modint r = 1;
    for (assert(b >= 0); b; b >>= 1, a *= a) if (b & 1) r *= a;
    return r;
  }
  friend int raw(const modint& self) { return self.v; }
  friend ostream& operator<<(ostream& os, const modint& self) { return os << raw(self); }
  explicit operator bool() const { return v != 0; }
};/*}}}*/
using mint = modint<998244353>;
int n;
mint _[2][60], *f = _[0] + 30, *g = _[1] + 30;
int mian() {
  cin >> n;
  memset(_, 0, sizeof _);
  g[0] = 1;
  mint ans = 0;
  bool flag = false;
  for (int i = 1; i <= n; i++) {
    swap(f, g);
    int lim = 25;
    for (int j = -lim - 1; j <= lim + 1; j++) g[j] = 0;
    for (int j = -lim; j <= lim; j++) if (f[j]) g[j + 1] += f[j], g[j - 1] += f[j];
    int nlim = max(2, 22 - i);
    int a, b;
    cin >> a >> b;
    if (a != -1) {
      if (a + b != i) flag = true;
      for (int j = -lim - 1; j <= lim + 1; j++) if (abs(j) != abs(a - b)) g[j] = 0;
    }
    if (i == n) {
      for (int j = -lim - 1; j <= lim + 1; j++) if (abs(j) >= nlim) ans += g[j];
    } else {
      for (int j = -lim - 1; j <= lim + 1; j++) if (abs(j) >= nlim) g[j] = 0;
    }
  }
  if (flag) ans = 0;
  cout << ans << endl;
  return 0;
}
int main() {
#ifndef LOCAL
  cin.tie(nullptr)->sync_with_stdio(false);
#endif
  int t;
  cin >> t;
  while (t--) mian();
  return 0;
}