#include<iostream>
#include<map>
#include<vector>
#include<algorithm>
#include<cassert>
#include<atcoder/modint>
#include<atcoder/lazysegtree>
using namespace std;
using mint=atcoder::modint998244353;
struct dat{
	mint sum;
	mint len;
};
dat op(dat l,dat r){return dat{l.sum+r.sum,l.len+r.len};}
dat e(){return dat{mint::raw(0),mint::raw(0)};}
dat mp(mint f,dat x)
{
	x.sum+=f*x.len;
	return x;
}
mint cmp(mint f,mint g){return f+g;}
mint id(){return mint::raw(0);}
int N;
int L[2<<17],R[2<<17];
int main()
{
	cin>>N;
	vector<int>vs;
	for(int i=0;i<N;i++)
	{
		cin>>L[i]>>R[i];
		vs.push_back(L[i]);
		vs.push_back(R[i]+1);
	}
	if(N==1)
	{
		cout<<0<<endl;
		return 0;
	}
	sort(vs.begin(),vs.end());
	vs.erase(unique(vs.begin(),vs.end()),vs.end());
	vector<dat>init(vs.size()-1);
	for(int i=0;i+1<vs.size();i++)
	{
		init[i].sum=mint::raw(0);
		init[i].len=mint::raw(vs[i+1]-vs[i]);
	}
	mint ans=(long)N*(N-1)/2;
	atcoder::lazy_segtree<dat,op,e,mint,mp,cmp,id>seg(init);
	for(int i=0;i<N;i++)
	{
		int l=lower_bound(vs.begin(),vs.end(),L[i])-vs.begin();
		int r=lower_bound(vs.begin(),vs.end(),R[i]+1)-vs.begin();
		mint coef=mint(R[i]-L[i]+1).inv();
		ans-=seg.prod(l,r).sum*coef;
		seg.apply(l,r,coef);
	}
	for(int i=1;i<=N;i++)ans*=mint::raw(i);
	ans/=2;
	cout<<ans.val()<<endl;
}