#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10;
const int mod=998244353;
pair<int,int>a[N];
vector<int>f[N<<2],g[N<<2];
int n;
int ksm(int x,int y){
	int ans=1;
	for (;y;y>>=1,x=1ll*x*x%mod) if (y&1) ans=1ll*ans*x%mod;
	return ans;
}
int main(){
	scanf("%d",&n);
	vector<int>w;
	for (int i=1;i<=n;i++) {
	scanf("%d%d",&a[i].first,&a[i].second);
	a[i].second++;
	w.push_back(a[i].first);
	w.push_back(a[i].second);
	}
	sort(w.begin(),w.end());
	int m=unique(w.begin(),w.end())-w.begin();
	w.resize(m);
	for (int i=1;i<=n;i++){
	 f[lower_bound(w.begin(),w.end(),a[i].first)-w.begin()].push_back(ksm(a[i].second-a[i].first,mod-2));
	 g[lower_bound(w.begin(),w.end(),a[i].second)-w.begin()].push_back(ksm(a[i].second-a[i].first,mod-2)); 
	}
	int x=0,x2=0;
	int ans=1ll*n*(n-1)/2%mod;
	int inv2=ksm(2,mod-2);
	for (int i=0;i<m-1;i++){
		for (int j=0;j<f[i].size();j++) x=(x+f[i][j])%mod,x2=(x2+1ll*f[i][j]*f[i][j]%mod)%mod;
		for (int j=0;j<g[i].size();j++) x=(x-g[i][j]+mod)%mod,x2=(x2-1ll*g[i][j]*g[i][j]%mod+mod)%mod;
		ans=(ans-1ll*(1ll*x*x%mod-x2+mod)%mod*inv2%mod*(w[i+1]-w[i])%mod+mod)%mod; 		
	} 
	for (int i=1;i<=n;i++) ans=1ll*ans*i%mod;
	ans=1ll*ans*ksm(2,mod-2)%mod;
	printf("%d\n",ans);
}