#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
const long long HALF = 499122177;
const long long QUARTER = 748683265;
long long modpow(long long a, long long b){
  long long ans = 1;
  while (b > 0){
    if (b % 2 == 1){
      ans *= a;
      ans %= MOD;
    }
    a *= a;
    a %= MOD;
    b /= 2;
  }
  return ans;
}
long long modinv(long long a){
  return modpow(a, MOD - 2);
}
int main(){
  int N;
  cin >> N;
  vector<int> B(N), C(N);
  for (int i = 0; i < N; i++){
    cin >> B[i] >> C[i];
    C[i]++;
  }
  vector<long long> W(N);
  for (int i = 0; i < N; i++){
    W[i] = modinv(C[i] - B[i]);
  }
  vector<int> X;
  for (int i = 0; i < N; i++){
    X.push_back(B[i]);
    X.push_back(C[i]);
  }
  sort(X.begin(), X.end());
  X.erase(unique(X.begin(), X.end()), X.end());
  int M = X.size();
  for (int i = 0; i < N; i++){
    B[i] = lower_bound(X.begin(), X.end(), B[i]) - X.begin();
    C[i] = lower_bound(X.begin(), X.end(), C[i]) - X.begin();
  }
  long long ans = (long long) N * (N - 1) / 2 % MOD * HALF % MOD;
  vector<long long> imos1(M + 1, 0), imos2(M + 1, 0);
  for (int i = 0; i < N; i++){
  	imos1[B[i]] += W[i];
  	imos1[B[i]] %= MOD;
  	imos1[C[i]] += MOD - W[i];
  	imos1[C[i]] %= MOD;
  	imos2[B[i]] += W[i] * W[i];
  	imos2[B[i]] %= MOD;
  	imos2[C[i]] += MOD - W[i] * W[i] % MOD;
  	imos2[C[i]] %= MOD;
  }
  for (int i = 0; i < M; i++){
  	imos1[i + 1] += imos1[i];
  	imos1[i + 1] %= MOD;
  	imos2[i + 1] += imos2[i];
  	imos2[i + 1] %= MOD;
  }
  for (int i = 0; i < M; i++){
  	ans += MOD - (imos1[i] * imos1[i] + MOD - imos2[i]) % MOD * QUARTER % MOD * (X[i + 1] - X[i]) % MOD;
  	ans %= MOD;
  }
  for (int i = 1; i <= N; i++){
    ans *= i;
    ans %= MOD;
  }
  cout << ans << endl;
}