#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N;
int B[202020],C[202020];

vector<int> add[404040];
vector<int> del[404040];
const ll mo=998244353;

ll modpow(ll a, ll n = mo-2) {
	ll r=1;a%=mo;
	while(n) r=r*((n%2)?a:1)%mo,a=a*a%mo,n>>=1;
	return r;
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N;
	vector<int> Xs={0};
	FOR(i,N) {
		cin>>B[i]>>C[i];
		C[i]++;
		Xs.push_back(B[i]);
		Xs.push_back(C[i]);
	}
	sort(ALL(Xs));
	Xs.erase(unique(ALL(Xs)),Xs.end());
	
	FOR(i,N) {
		x=lower_bound(ALL(Xs),B[i])-Xs.begin();
		y=lower_bound(ALL(Xs),C[i])-Xs.begin();
		add[x].push_back(modpow(C[i]-B[i]));
		del[y].push_back(modpow(C[i]-B[i]));
	}
	
	ll ret=1LL*N*(N-1)%mo*modpow(4)%mo;
	ll sum1=0,sum2=0;
	FOR(i,Xs.size()) {
		FORR(d,del[i]) {
			(sum1+=mo-d)%=mo;
			(sum2+=mo-sum1*d)%=mo;
		}
		FORR(d,add[i]) {
			(sum2+=sum1*d)%=mo;
			(sum1+=d)%=mo;
		}
		if(sum2) {
			(ret+=mo-sum2*(Xs[i+1]-Xs[i])%mo*modpow(2)%mo)%=mo;
		}
	}
	FOR(i,N) ret=ret*(i+1)%mo;
	cout<<ret<<endl;
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}