#include <bits/stdc++.h>
using namespace std;
using ll = long long;

template <class T>
using vc = vector<T>;
template <class T>
using vvc = vector<vc<T>>;
template <class T>
using vvvc = vector<vvc<T>>;
template <class T>
using vvvvc = vector<vvvc<T>>;
template <class T>
using vvvvvc = vector<vvvvc<T>>;

#define vv(type, name, h, w) vector<vector<type>> name(h, vector<type>(w, type(0)))
#define vvv(type, name, h, w, l) vector<vector<vector<type>>> name(h, vector<vector<type>>(w, vector<type>(l, type(0))))
#define vvvv(type, name, a, b, c, d) vector<vector<vector<vector<type>>>> name(a, vector<vector<vector<type>>>(b, vector<vector<type>>(c, vector<type>(d, type(0)))))

#define elif else if

#define FOR1(a) for (ll _ = 0; _ < ll(a); _++)
#define FOR2(i,n) for (ll i = 0; i < ll(n); i++)
#define FOR3(i,l,r) for (ll i = l; i < ll(r); i++)
#define FOR4(i,l,r,c) for (ll i = l; i < ll(r); i += (c))
#define FOR1_R(a) for (ll _ = ll(a) - 1; _ >= 0; _--)
#define FOR2_R(i,n) for (ll i = (n) - 1; i >= ll(0); i--)
#define FOR3_R(i,l,r) for (ll i = (r) - 1; i >= ll(l); i--)
#define FOR4_R(i,l,r,c) for (ll i = (r) - 1; i >= ll(l); i -= (c))
#define overload4(a, b, c, d, e, ...) e
#define FOR(...) overload4(__VA_ARGS__, FOR4, FOR3, FOR2, FOR1)(__VA_ARGS__)
#define FOR_R(...) overload4(__VA_ARGS__, FOR4_R, FOR3_R, FOR2_R, FOR1_R)(__VA_ARGS__)
#define FOR_in(a, A) for (auto a: A)
#define FOR_each(a, A) for (auto &&a: A)
#define FOR_subset(t,s) for(ll t = (s); t >= 0; t = (t == 0 ? -1 : (t - 1) & (s)))

#define all(x) x.begin(), x.end()
#define len(x) ll(x.size())

int popcnt(int x) { return __builtin_popcount(x); }
int popcnt(uint32_t x) { return __builtin_popcount(x); }
int popcnt(long long x) { return __builtin_popcountll(x); }
int popcnt(uint64_t x) { return __builtin_popcountll(x); }
int topbit(int x) { return (x == 0 ? -1 : 31 - __builtin_clz(x)); }
int topbit(uint32_t x) { return (x == 0 ? -1 : 31 - __builtin_clz(x)); }
int topbit(long long x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); }
int topbit(uint64_t x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); }

// 入力
void rd() {}
void rd(char& c) { cin >> c; }
void rd(string& s) { cin >> s; }
void rd(int& x) { cin >> x; }
void rd(uint32_t& x) { cin >> x; }
void rd(long long& x) { cin >> x; }
void rd(uint64_t& x) { cin >> x; }
template<class T>
void rd(vector<T> & v) {
  for (auto& x:v) rd(x);
}

void read() {}
template <class H, class... T>
void read(H& h, T&... t) {
  rd(h), read(t...);
}

#define CHAR(...) \
  char __VA_ARGS__; \
  read(__VA_ARGS__)

#define STRING(...) \
  string __VA_ARGS__; \
  read(__VA_ARGS__)

#define INT(...) \
  int __VA_ARGS__; \
  read(__VA_ARGS__)

#define U32(...) \
  uint32_t __VA_ARGS__; \
  read(__VA_ARGS__)

#define LL(...) \
  long long __VA_ARGS__; \
  read(__VA_ARGS__)

#define U64(...) \
  uint64_t __VA_ARGS__; \
  read(__VA_ARGS__)

#define VC(t, a, n) \
  vector<t> a(n); \
  read(a)

#define VVC(t, a, h, w) \
  vector<vector<t>> a(h, vector<t>(w)); \
  read(a)

//出力
void wt() {}
void wt(const char c) { cout << c; }
void wt(const string s) { cout << s; }
void wt(int x) { cout << x; }
void wt(uint32_t x) { cout << x; }
void wt(long long x) { cout << x; }
void wt(uint64_t x) { cout << x; }
template<class T>
void wt(const vector<T> v){
  int n = v.size();
  for (int i = 0; i < n; i++){
    if (i) wt(' ');
    wt(v[i]);
  }
}

void print() { wt('\n'); }
template <class Head, class... Tail>
void print(Head&& head, Tail&&... tail) {
  wt(head);
  if (sizeof...(Tail)) wt(' ');
  print(forward<Tail>(tail)...);
}

template <int mod>
struct modint {
  static constexpr uint32_t umod = uint32_t(mod);
  static_assert(umod < (uint32_t(1) << 31));
  uint32_t val;

  static modint raw(uint32_t v) {
    modint x;
    x.val = v % mod;
    return x;
  }

  constexpr modint() : val(0) {}
  constexpr modint(uint32_t x) : val(x % umod) {}
  constexpr modint(uint64_t x) : val(x % umod) {}
  constexpr modint(unsigned __int128 x) : val(x % umod) {}
  constexpr modint(int x) : val((x %= mod) < 0 ? x + mod : x) {};
  constexpr modint(long long x) : val((x %= mod) < 0 ? x + mod : x) {};
  constexpr modint(__int128 x) : val((x %= mod) < 0 ? x + mod : x) {};

  bool operator<(const modint &other) const { return val < other.val; }
  modint &operator+=(const modint &p) {
    if ((val += p.val) >= umod) val -= umod;
    return *this;
  }
  modint &operator-=(const modint &p) {
    if ((val += umod - p.val) >= umod) val -= umod;
    return *this;
  }
  modint &operator*=(const modint &p) {
    val = uint64_t(val) * p.val % umod;
    return *this;
  }
  modint &operator/=(const modint &p) {
    *this *= p.inverse();
    return *this;
  }
  modint operator-() const { return modint::raw(val ? mod - val : uint32_t(0)); }
  modint operator+(const modint &p) const { return modint(*this) += p; }
  modint operator-(const modint &p) const { return modint(*this) -= p; }
  modint operator*(const modint &p) const { return modint(*this) *= p; }
  modint operator/(const modint &p) const { return modint(*this) /= p; }
  bool operator==(const modint &p) const { return val == p.val; }
  bool operator!=(const modint &p) const { return val != p.val; }

  modint inverse() const {
    int a = val, b = mod, s = 1, t = 0;
    while (1) {
      if (a == 1) return modint(s);
      t -= (b / a) * s;
      b %= a;
      if (b == 1) return modint(t + mod);
      s -= (a / b) * t;
      a %= b;
    }
  }

  modint pow(long long n) const {
    assert(n >= 0);
    modint res(1), a(val);
    while (n > 0) {
      if (n & 1) res *= a;
      a *= a;
      n >>= 1;
    }
    return res;
  }

  static constexpr int get_mod() { return mod; }
  
  static constexpr pair<int,int> ntt_info() {
    if (mod == 167772161) return {25,17};
    if (mod == 469762049) return {26,30};
    if (mod == 754974721) return {24,362};
    if (mod == 880803841) return {23,211};
    if (mod == 998244353) return {23,31};
    return {-1, -1};
  }
};

template <int mod>
void rd(modint<mod>& x) {
  uint32_t y;
  cin >> y;
  x = y;
}

template <int mod>
void wt(modint<mod> x){
  wt(x.val);
}

template <typename mint>
mint fact(long long n) {
  static vector<mint> res = {1, 1};
  static long long le = 1;
  while (le <= n){
    le++;
    res.push_back(res[le - 1] * le);
  }
  return res[n];
}

template <typename mint>
mint fact_inv(long long n) {
  static vector<mint> res = {1, 1};
  static long long le = 1;
  while (le <= n){
    le++;
    res.push_back(res[le - 1] / le);
  }
  return res[n];
}

using mint = modint<998244353>;

int main() {
  INT(K);
  int S = 0;
  mint ans = mint(1);
  FOR(K) {
    INT(L, M);
    ans *= fact_inv<mint>(L).pow(M);
    ans *= fact_inv<mint>(M);
    S += L * M;
  }
  ans *= fact<mint>(S);
  print(ans);
}