// g++-13 1.cpp -std=c++17 -O2 -I .
#include <bits/stdc++.h>
using namespace std;

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#include<ext/pb_ds/tag_and_trait.hpp>
using namespace __gnu_pbds;

#include <atcoder/all>
using namespace atcoder;

using ll = long long;
using ld = long double;
 
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vld = vector<ld>;
using vvld = vector<vld>;
using vst = vector<string>;
using vvst = vector<vst>;
 
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define pq_big(T) priority_queue<T,vector<T>,less<T>>
#define pq_small(T) priority_queue<T,vector<T>,greater<T>>
#define all(a) a.begin(),a.end()
#define rep(i,start,end) for(ll i=start;i<(ll)(end);i++)
#define per(i,start,end) for(ll i=start;i>=(ll)(end);i--)
#define uniq(a) sort(all(a));a.erase(unique(all(a)),a.end())

using mint = modint998244353;

random_device seed;
mt19937_64 randint(seed());

ll grr(ll mi, ll ma) { // [mi, ma)
    return mi + randint() % (ma - mi);
}

mint sub(ll l,ll r,ll a,ll b){
  // l <= i <= r について max(b - max(a - 1, i), 0) を足し
  // 最後に (r - l + 1) * (b - a + 1) で割る
  // i < a => b - a + 1
  // a <= i <= b => b - i
  // b < i => 0

  mint res=0;
  res+=(b-a+1)*max(0LL,a-l);
  if(b<=l){
    return (mint)0;
  }
  if(r<a){
    return (mint)1;
  }

  ll p=min(b-a,b-l),q=max(0LL,b-r);
  res+=(p+q)*(p-q+1)/2;

  res/=(r-l+1);
  res/=(b-a+1);
  return res;
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;cin>>n;
  ll l,r;cin>>l>>r;
  mint ans=0;

  rep(i,0,n-1){
    ll a,b;cin>>a>>b;
    ans+=sub(l,r,a,b);
  }
  ans++;

  cout<<ans.val()<<endl;
}