pub use __cargo_equip::prelude::*;

use modint::ModInt998244353 as Mint;
#[allow(unused_imports)]
use proconio::{
    input,
    marker::{Bytes, Chars, Usize1},
};

fn main() {
    input! {
        n: usize,
        lr: [(usize, usize); n],
    }
    let (l0, r0) = lr[0];
    let mut res = Mint::new(1);
    for &(l1, r1) in &lr[1..] {
        if r1 <= l0 {
            continue;
        }
        if r0 < l1 {
            res += 1;
            continue;
        }
        if r0 < r1 {
            res += Mint::new(r1 - r0) / (r1 - l1 + 1);
        }
        let w = (r0 - l0) + (r1 - l1) - (r0.max(r1) - l0.min(l1)) + 1;
        if w > 0 {
            res += Mint::new(w * (w - 1) / 2) / (r0 - l0 + 1) / (r1 - l1 + 1);
        }
    }
    println!("{}", res);
}

// The following code was expanded by `cargo-equip`.

///  # Bundled libraries
/// 
///  - `algebraic 0.1.0 (path+████████████████████████████████████████████████████████)` published in **missing** licensed under `CC0-1.0` as `crate::__cargo_equip::crates::algebraic`
///  - `modint 0.1.0 (path+█████████████████████████████████████████████████████████)`   published in **missing** licensed under `CC0-1.0` as `crate::__cargo_equip::crates::modint`
#[cfg_attr(any(), rustfmt::skip)]
#[allow(unused)]
mod __cargo_equip {
    pub(crate) mod crates {
        pub mod algebraic {pub use crate::__cargo_equip::macros::algebraic::*;pub trait Algebra{type S;}pub trait Act:Algebra{type X;fn act(f:&Self::S,x:&Self::X)->Self::X;}pub trait Monoid:Algebra{fn e()->Self::S;fn op(x:&Self::S,y:&Self::S)->Self::S;}pub trait Group:Monoid{fn inv(x:&Self::S)->Self::S;}pub trait Zero{fn zero()->Self;fn is_zero(&self)->bool;}pub trait One{fn one()->Self;fn is_one(&self)->bool;}#[macro_export]macro_rules!__cargo_equip_macro_def_algebraic_algebra{($ident:ident,$ty:ty)=>{#[derive(Clone)]enum$ident{}impl$crate::__cargo_equip::crates::algebraic::Algebra for$ident{type S=$ty;}};}macro_rules!algebra{($($tt:tt)*)=>(crate::__cargo_equip_macro_def_algebraic_algebra!{$($tt)*})}#[macro_export]macro_rules!__cargo_equip_macro_def_algebraic_act{($ident:ident,$tar:ty,$act:expr)=>{impl$crate::__cargo_equip::crates::algebraic::Act for$ident{type X=$tar;#[inline]fn act(f:&Self::S,x:&Self::X)->Self::X{$act(f,x)}}};}macro_rules!act{($($tt:tt)*)=>(crate::__cargo_equip_macro_def_algebraic_act!{$($tt)*})}#[macro_export]macro_rules!__cargo_equip_macro_def_algebraic_monoid{($ident:ident,$e:expr,$op:expr)=>{impl$crate::__cargo_equip::crates::algebraic::Monoid for$ident{#[inline]fn e()->Self::S{$e}#[inline]fn op(x:&Self::S,y:&Self::S)->Self::S{$op(x,y)}}};}macro_rules!monoid{($($tt:tt)*)=>(crate::__cargo_equip_macro_def_algebraic_monoid!{$($tt)*})}#[macro_export]macro_rules!__cargo_equip_macro_def_algebraic_group{($ident:ident,$e:expr,$op:expr,$inv:expr)=>{impl$crate::__cargo_equip::crates::algebraic::Monoid for$ident{#[inline]fn e()->Self::S{$e}#[inline]fn op(x:&Self::S,y:&Self::S)->Self::S{$op(x,y)}}impl$crate::__cargo_equip::crates::algebraic::Group for$ident{#[inline]fn inv(x:&Self::S)->Self::S{$inv(x)}}};}macro_rules!group{($($tt:tt)*)=>(crate::__cargo_equip_macro_def_algebraic_group!{$($tt)*})}macro_rules!impl_zero_one{($($t:ty)*)=>{$(impl$crate::__cargo_equip::crates::algebraic::Zero for$t{fn zero()->Self{0}fn is_zero(&self)->bool{*self==0}}impl$crate::__cargo_equip::crates::algebraic::One for$t{fn one()->Self{1}fn is_one(&self)->bool{*self==1}})*};}impl_zero_one!(usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128);}
        pub mod modint {use crate::__cargo_equip::preludes::modint::*;use std::{fmt,hash::Hash,iter::{Product,Sum},num::ParseIntError,ops::{Add,AddAssign,Div,DivAssign,Mul,MulAssign,Neg,Sub,SubAssign},str::FromStr,sync::atomic::{self,AtomicU32,AtomicU64},};use algebraic::{One,Zero};#[derive(Clone,Copy,Default,PartialEq,Eq,Hash)]#[repr(transparent)]pub struct StaticModInt<const P:u32>(u32);#[derive(Clone,Copy,Default,PartialEq,Eq,Hash)]#[repr(transparent)]pub struct DynamicModInt(u32);pub type ModInt998244353=StaticModInt<998_244_353>;pub type ModInt1000000007=StaticModInt<1_000_000_007>;pub trait ModInt:Default+Zero+One+FromStr+From<i8>+From<i16>+From<i32>+From<i64>+From<i128>+From<isize>+From<u8>+From<u16>+From<u32>+From<u64>+From<u128>+From<usize>+Copy+Eq+Hash+fmt::Display+fmt::Debug+Neg<Output=Self>+Add<Output=Self>+Sub<Output=Self>+Mul<Output=Self>+Div<Output=Self>+AddAssign+SubAssign+MulAssign+DivAssign{fn modulus()->u32;fn raw(val:u32)->Self;fn val(self)->u32;fn inv(self)->Self;fn pow(self,k:usize)->Self;fn sqrt(self)->Option<Self>;}const fn mul(x:u32,y:u32,m:u32)->u32{(x as u64*y as u64%m as u64)as u32}const fn pow(x:u32,mut n:u32,m:u32)->u32{if m==1{return 0;}let mut r=1u64;let mut y=(x%m)as u64;while n!=0{if n&1!=0{r=r*y%m as u64;}y=y*y%m as u64;n>>=1;}r as u32}const fn is_prime(n:u32)->bool{match n{_ if n<=1=>return false,2|7|61=>return true,_ if n&1==0=>return false,_=>{}}let mut d=n-1;while d&1==0{d>>=1;}let a=[2,7,61];let mut i=0;while i<3{let mut t=d;let mut y=pow(a[i],t,n);while t!=n-1&&y!=1&&y!=n-1{y=(y as u64*y as u64%n as u64)as u32;t<<=1;}if y!=n-1&&t&1==0{return false;}i+=1;}true}const fn extgcd(mut a:u32,b:u32)->(u32,u32){a=a%b;if a==0{return(b,0);}let mut s=b as i64;let mut t=a as i64;let mut m0=0;let mut m1=1;while t!=0{let u=s/t;s-=t*u;m0-=m1*u;let tmp=s;s=t;t=tmp;let tmp=m0;m0=m1;m1=tmp;}if m0<0{m0+=b as i64/s;}(s as u32,m0 as u32)}const fn primitive_root(m:u32)->u32{match m{2=>return 1,167_772_161=>return 3,469_762_049=>return 3,754_974_721=>return 11,998_244_353=>return 3,_=>{}}let mut divs=[0;20];divs[0]=2;let mut cnt=1;let mut x=(m-1)/2;while x%2==0{x/=2;}let mut i=3;while i<std::u32::MAX{if i as u64*i as u64>x as u64{break;}if x%i==0{divs[cnt]=i;cnt+=1;while x%i==0{x/=i;}}i+=2;}if x>1{divs[cnt]=x;cnt+=1;}let mut g=2;loop{let mut i=0;while i<cnt{if pow(g,(m-1)/divs[i],m)==1{break;}i+=1;}if i==cnt{break g;}g+=1;}}const fn ntt_info(m:u32,)->(u32,usize,[u32;30],[u32;30],[u32;30],[u32;30],[u32;30],[u32;30],){let g=primitive_root(m);let rank2=(m-1).trailing_zeros()as usize;let mut root=[0;30];let mut iroot=[0;30];let mut rate2=[0;30];let mut irate2=[0;30];let mut rate3=[0;30];let mut irate3=[0;30];root[rank2]=pow(g,(m-1)>>rank2,m);iroot[rank2]=extgcd(root[rank2],m).1;let mut i=rank2;while i>0{i-=1;root[i]=mul(root[i+1],root[i+1],m);iroot[i]=mul(iroot[i+1],iroot[i+1],m);}let mut prod=1;let mut iprod=1;let mut i=0;while i+2<=rank2{rate2[i]=mul(root[i+2],prod,m);irate2[i]=mul(iroot[i+2],iprod,m);prod=mul(prod,iroot[i+2],m);iprod=mul(iprod,root[i+2],m);i+=1;}let mut prod=1;let mut iprod=1;let mut i=0;while i+3<=rank2{rate3[i]=mul(root[i+3],prod,m);irate3[i]=mul(iroot[i+3],iprod,m);prod=mul(prod,iroot[i+3],m);iprod=mul(iprod,root[i+3],m);i+=1;}(g,rank2,root,iroot,rate2,irate2,rate3,irate3)}fn rat_convert(x:u64,m:u64,d:u64)->Option<(u64,u64)>{let n=m/(2*d);if x<n&&1<d{return Some((x,1));}let mut l=(0,1);let mut r=(1,0);loop{let num=l.0+r.0;let den=l.1+r.1;let(i,q)=match(num*m).cmp(&(den*x)){std::cmp::Ordering::Less=>{let k=(x*l.1-m*l.0-1)/(m*r.0-x*r.1);l.0+=k*r.0;l.1+=k*r.1;l}std::cmp::Ordering::Equal=>return None,std::cmp::Ordering::Greater=>{let k=(m*r.0-x*r.1-1)/(x*l.1-m*l.0);r.0+=k*l.0;r.1+=k*l.1;r}};if q*x<i*m{continue;}let p=q*x-i*m;if p<n&&q<d{return Some((p,q));}}}impl<const P:u32>ModInt for StaticModInt<P>{#[inline(always)]fn modulus()->u32{P}#[inline]fn raw(val:u32)->Self{Self(val)}#[inline]fn val(self)->u32{self.0}#[inline]fn inv(self)->Self{self.inv()}fn pow(self,k:usize)->Self{self.pow(k)}fn sqrt(self)->Option<Self>{self.sqrt()}}impl<const P:u32>StaticModInt<P>{#[inline]pub fn new<T:Into<StaticModInt<P>>>(x:T)->Self{x.into()}#[inline(always)]pub fn modulus()->u32{P}#[inline]pub fn raw(val:u32)->Self{Self(val)}#[inline]pub fn val(self)->u32{self.0}#[inline]pub fn inv(self)->Self{assert_ne!(self.0,0);self.pow(P as usize-2)}pub fn pow(mut self,mut k:usize)->Self{let mut res=Self::from(1);while k!=0{if k&1!=0{res*=self;}k>>=1;self*=self;}res}pub fn sqrt(self)->Option<Self>{let p=Self::modulus()as usize;if self.val()<2{return Some(self);}else if self.pow(p-1>>1).val()!=1{return None;}let mut b=Self::from(1);while b.pow((p-1>>1)as usize).val()==1{b+=1;}let mut e=(p-1).trailing_zeros()as usize;let m=(p-1)>>e;let mut x=self.pow(m-1>>1);let mut y=self*x*x;x*=self;let mut z=b.pow(m);while y.val()!=1{let mut j=0;let mut t=y;while t.val()!=1{j+=1;t*=t;}z=z.pow(1<<e-j-1);x*=z;z*=z;y*=z;e=j;}Some(x)}}impl ModInt for DynamicModInt{#[inline(always)]fn modulus()->u32{BARRETT.modulus()}#[inline]fn raw(val:u32)->Self{Self(val)}#[inline]fn val(self)->u32{self.0}#[inline]fn inv(self)->Self{self.inv()}fn pow(self,k:usize)->Self{self.pow(k)}fn sqrt(self)->Option<Self>{self.sqrt()}}impl DynamicModInt{#[inline]pub fn new<T:Into<DynamicModInt>>(x:T)->Self{x.into()}#[inline(always)]pub fn modulus()->u32{BARRETT.modulus()}#[inline]pub fn raw(val:u32)->Self{Self(val)}#[inline]pub fn val(self)->u32{self.0}#[inline]pub fn inv(self)->Self{let(g,x)=extgcd(self.0,Self::modulus());assert_eq!(g,1);Self(x)}pub fn pow(mut self,mut k:usize)->Self{let mut res=Self::from(1);while k!=0{if k&1!=0{res*=self;}k>>=1;self*=self;}res}pub fn sqrt(self)->Option<Self>{let p=Self::modulus()as usize;if self.val()<2{return Some(self);}else if self.pow(p-1>>1).val()!=1{return None;}let mut b=Self::from(1);while b.pow((p-1>>1)as usize).val()==1{b+=1;}let mut e=(p-1).trailing_zeros()as usize;let m=(p-1)>>e;let mut x=self.pow(m-1>>1);let mut y=self*x*x;x*=self;let mut z=b.pow(m);while y.val()!=1{let mut j=0;let mut t=y;while t.val()!=1{j+=1;t*=t;}z=z.pow(1<<e-j-1);x*=z;z*=z;y*=z;e=j;}Some(x)}pub fn set_modulus(modulus:u32){BARRETT.set(modulus)}}struct Barrett{m:AtomicU32,im:AtomicU64,}impl Barrett{const fn new(m:u32)->Self{Self{m:AtomicU32::new(m),im:AtomicU64::new((!0/m as u64).wrapping_add(1)),}}#[inline]fn set(&self,m:u32){let im=(!0/m as u64).wrapping_add(1);self.m.store(m,atomic::Ordering::SeqCst);self.im.store(im,atomic::Ordering::SeqCst);}#[inline]fn modulus(&self)->u32{self.m.load(atomic::Ordering::SeqCst)}#[inline]fn mul(&self,a:u32,b:u32)->u32{let m=self.m.load(atomic::Ordering::SeqCst);let im=self.im.load(atomic::Ordering::SeqCst);let mut z=a as u64;z*=b as u64;let x=(((z as u128)*(im as u128))>>64)as u64;let mut v=z.wrapping_sub(x.wrapping_mul(m as u64))as u32;if m<=v{v=v.wrapping_add(m);}v}}static BARRETT:Barrett=Barrett::new(998_244_353);impl<const P:u32>FromStr for StaticModInt<P>{type Err=ParseIntError;fn from_str(s:&str)->Result<Self,Self::Err>{s.parse::<i64>().map(Self::from)}}impl FromStr for DynamicModInt{type Err=ParseIntError;fn from_str(s:&str)->Result<Self,Self::Err>{s.parse::<i64>().map(Self::from)}}impl<const P:u32>fmt::Display for StaticModInt<P>{fn fmt(&self,f:&mut fmt::Formatter<'_>)->fmt::Result{write!(f,"{}",self.0)}}impl fmt::Display for DynamicModInt{fn fmt(&self,f:&mut fmt::Formatter<'_>)->fmt::Result{write!(f,"{}",self.0)}}impl<const P:u32>fmt::Debug for StaticModInt<P>{fn fmt(&self,f:&mut fmt::Formatter<'_>)->fmt::Result{if let Some((num,den))=rat_convert(self.0 as u64,P as u64,1025){write!(f,"{}",num)?;if den!=1{write!(f,"/{}",den)?;}}else if let Some((num,den))=rat_convert((P-self.0)as u64,P as u64,1025){write!(f,"-{}",num)?;if den!=1{write!(f,"/{}",den)?;}}else{write!(f,"{}",self.0)?;}Ok(())}}impl fmt::Debug for DynamicModInt{fn fmt(&self,f:&mut fmt::Formatter<'_>)->fmt::Result{write!(f,"{}",self.0)}}macro_rules!impl_from_integer{($(($t1:ty,$t2:ty)),*)=>{$(impl<const P:u32>From<$t1>for StaticModInt<P>{fn from(x:$t1)->Self{Self((x as$t2).rem_euclid(P as$t2)as u32)}}impl From<$t1>for DynamicModInt{fn from(x:$t1)->Self{Self((x as$t2).rem_euclid(Self::modulus()as$t2)as u32)}})*};}impl_from_integer!((i8,i32),(i16,i32),(i32,i32),(i64,i64),(isize,i64),(i128,i128),(u8,u32),(u16,u32),(u32,u32),(u64,u64),(usize,u64),(u128,u128));impl<const P:u32,T:Into<Self>>AddAssign<T>for StaticModInt<P>{fn add_assign(&mut self,rhs:T){self.0+=rhs.into().0;if self.0>=P{self.0-=P;}}}impl<T:Into<Self>>AddAssign<T>for DynamicModInt{fn add_assign(&mut self,rhs:T){self.0+=rhs.into().0;if self.0>=Self::modulus(){self.0-=Self::modulus();}}}impl<const P:u32,T:Into<Self>>SubAssign<T>for StaticModInt<P>{fn sub_assign(&mut self,rhs:T){let rhs=rhs.into().0;if self.0<rhs{self.0+=P;}self.0-=rhs;}}impl<T:Into<Self>>SubAssign<T>for DynamicModInt{fn sub_assign(&mut self,rhs:T){let rhs=rhs.into().0;if self.0<rhs{self.0+=Self::modulus();}self.0-=rhs;}}impl<const P:u32,T:Into<Self>>MulAssign<T>for StaticModInt<P>{fn mul_assign(&mut self,rhs:T){*self=Self((self.0 as u64*rhs.into().0 as u64%P as u64)as u32);}}impl<T:Into<Self>>MulAssign<T>for DynamicModInt{fn mul_assign(&mut self,rhs:T){*self=Self(BARRETT.mul(self.0,rhs.into().0));}}impl<const P:u32,T:Into<Self>>DivAssign<T>for StaticModInt<P>{fn div_assign(&mut self,rhs:T){*self*=rhs.into().inv()}}impl<T:Into<Self>>DivAssign<T>for DynamicModInt{fn div_assign(&mut self,rhs:T){*self=*self*rhs.into().inv()}}impl<const P:u32>Neg for StaticModInt<P>{type Output=Self;fn neg(self)->Self::Output{if self.0==0{Self(0)}else{Self(P-self.0)}}}impl Neg for DynamicModInt{type Output=Self;fn neg(self)->Self::Output{if self.0==0{Self(0)}else{Self(Self::modulus()-self.0)}}}impl<const P:u32>Neg for&StaticModInt<P>{type Output=StaticModInt<P>;fn neg(self)->Self::Output{if self.0==0{StaticModInt(0)}else{StaticModInt(P-self.0)}}}impl Neg for&DynamicModInt{type Output=DynamicModInt;fn neg(self)->Self::Output{if self.0==0{DynamicModInt(0)}else{DynamicModInt(DynamicModInt::modulus()-self.0)}}}macro_rules!impl_ops{($($trait:ident,$trait_assign:ident,$fn:ident,$fn_assign:ident,)*)=>{$(impl<const P:u32>$trait_assign<&StaticModInt<P>>for StaticModInt<P>{fn$fn_assign(&mut self,rhs:&StaticModInt<P>){self.$fn_assign(*rhs);}}impl<const P:u32,T:Into<StaticModInt<P>>>$trait<T>for StaticModInt<P>{type Output=StaticModInt<P>;fn$fn(mut self,rhs:T)->Self::Output{self.$fn_assign(rhs.into());self}}impl<const P:u32>$trait<&StaticModInt<P>>for StaticModInt<P>{type Output=StaticModInt<P>;fn$fn(self,rhs:&StaticModInt<P>)->Self::Output{self.$fn(*rhs)}}impl<const P:u32,T:Into<StaticModInt<P>>>$trait<T>for&StaticModInt<P>{type Output=StaticModInt<P>;fn$fn(self,rhs:T)->Self::Output{(*self).$fn(rhs.into())}}impl<const P:u32>$trait<&StaticModInt<P>>for&StaticModInt<P>{type Output=StaticModInt<P>;fn$fn(self,rhs:&StaticModInt<P>)->Self::Output{(*self).$fn(*rhs)}}impl$trait_assign<&DynamicModInt>for DynamicModInt{fn$fn_assign(&mut self,rhs:&DynamicModInt){self.$fn_assign(*rhs);}}impl<T:Into<DynamicModInt>>$trait<T>for DynamicModInt{type Output=DynamicModInt;fn$fn(mut self,rhs:T)->Self::Output{self.$fn_assign(rhs.into());self}}impl$trait<&DynamicModInt>for DynamicModInt{type Output=DynamicModInt;fn$fn(self,rhs:&DynamicModInt)->Self::Output{self.$fn(*rhs)}}impl<T:Into<DynamicModInt>>$trait<T>for&DynamicModInt{type Output=DynamicModInt;fn$fn(self,rhs:T)->Self::Output{(*self).$fn(rhs.into())}}impl$trait<&DynamicModInt>for&DynamicModInt{type Output=DynamicModInt;fn$fn(self,rhs:&DynamicModInt)->Self::Output{(*self).$fn(*rhs)}})*};}impl_ops!{Add,AddAssign,add,add_assign,Sub,SubAssign,sub,sub_assign,Mul,MulAssign,mul,mul_assign,Div,DivAssign,div,div_assign,}impl<const P:u32>Sum for StaticModInt<P>{fn sum<I:Iterator<Item=Self>>(iter:I)->Self{iter.fold(Self::raw(0),|b,x|b+x)}}impl<const P:u32>Product for StaticModInt<P>{fn product<I:Iterator<Item=Self>>(iter:I)->Self{iter.fold(Self::from(1),|b,x|b*x)}}impl<'a,const P:u32>Sum<&'a Self>for StaticModInt<P>{fn sum<I:Iterator<Item=&'a Self>>(iter:I)->Self{iter.fold(Self::raw(0),|b,x|b+x)}}impl<'a,const P:u32>Product<&'a Self>for StaticModInt<P>{fn product<I:Iterator<Item=&'a Self>>(iter:I)->Self{iter.fold(Self::from(1),|b,x|b*x)}}impl<const P:u32>StaticModInt<P>{pub const G:u32=ntt_info(P).0;pub const RANK2:usize=ntt_info(P).1;pub const ROOT:[u32;30]=ntt_info(P).2;pub const IROOT:[u32;30]=ntt_info(P).3;pub const RATE2:[u32;30]=ntt_info(P).4;pub const IRATE2:[u32;30]=ntt_info(P).5;pub const RATE3:[u32;30]=ntt_info(P).6;pub const IRATE3:[u32;30]=ntt_info(P).7;pub const IS_NTT_FRIENDLY:bool=is_prime(P)&&Self::RANK2>=21;}impl<const P:u32>Zero for StaticModInt<P>{fn zero()->Self{Self(0)}fn is_zero(&self)->bool{self.0==0}}impl<const P:u32>One for StaticModInt<P>{fn one()->Self{Self::new(1)}fn is_one(&self)->bool{self==&Self::one()}}impl Zero for DynamicModInt{fn zero()->Self{Self(0)}fn is_zero(&self)->bool{self.0==0}}impl One for DynamicModInt{fn one()->Self{Self::new(1)}fn is_one(&self)->bool{self==&Self::one()}}}
    }

    pub(crate) mod macros {
        pub mod algebraic {pub use crate::{__cargo_equip_macro_def_algebraic_act as act,__cargo_equip_macro_def_algebraic_algebra as algebra,__cargo_equip_macro_def_algebraic_group as group,__cargo_equip_macro_def_algebraic_monoid as monoid};}
        pub mod modint {}
    }

    pub(crate) mod prelude {pub use crate::__cargo_equip::crates::*;}

    mod preludes {
        pub mod algebraic {}
        pub mod modint {pub(in crate::__cargo_equip)use crate::__cargo_equip::crates::algebraic;}
    }
}