#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
const ll MOD=1e9+7;
ll powmod(ll a, ll k){
    ll ap=a, ans=1;
    while(k){
        if(k&1){
            ans*=ap;
            ans%=MOD;
        }
        ap=ap*ap;
        ap%=MOD;
        k>>=1;
    }
    return ans;
}
ll inv(ll a){
    return powmod(a, MOD-2);
}
int main()
{
	int n;
	cin>>n;
	int a[220], b[220];
	vector<int> v;
	for(int i=0; i<n; i++){
		cin>>a[i]>>b[i];
		v.push_back(a[i]);
      	v.push_back(b[i]);
	}
	ll invs[404];
	for(int i=1; i<=2*n; i++) invs[i]=inv(i);
	sort(v.begin(), v.end());
	v.erase(unique(v.begin(), v.end()), v.end());
	int m=v.size();
	vector<ll> p[202][402];
	for(int i=0; i<m-1; i++) p[n][i].push_back(1);
	ll ans=0;
	for(int i=n-1; i>=0; i--){
		ll s[404];
		ll tot=0;
		for(int j=0; j<m-1; j++){
			int l=v[j], r=v[j+1];
			if(!(a[i]<=l && r<=b[i])){
				s[j]=0;
				continue;
			}
			s[j]=0;
			ll pp=r;
			for(int k=0; k<p[i+1][j].size(); k++){
				(s[j]+=p[i+1][j][k]*pp%MOD*invs[k+1])%=MOD;
				(pp*=r)%=MOD;
			}
			pp=l;
			for(int k=0; k<p[i+1][j].size(); k++){
				(s[j]+=MOD-p[i+1][j][k]*pp%MOD*invs[k+1]%MOD)%=MOD;
				(pp*=l)%=MOD;
			}
			(tot+=s[j])%=MOD;
		}
		if(i==0){
			ans=tot;
			break;
		}
		for(int j=0; j<m-1; j++){
			int l=v[j], r=v[j+1];
			if(i&1){
				if(l>=b[i]) p[i][j].push_back(0);
				else if(l>=a[i]){
					p[i][j].resize(p[i+1][j].size()+1);
					for(int k=j+1; k<m-1; k++){
						(p[i][j][0]+=s[k])%=MOD;
					}
					ll pp=r;
					for(int k=0; k<p[i+1][j].size(); k++){
						(p[i][j][0]+=p[i+1][j][k]*pp%MOD*invs[k+1])%=MOD;
						(pp*=r)%=MOD;
						(p[i][j][k+1]+=MOD-p[i+1][j][k]*invs[k+1]%MOD)%=MOD;
					}
				}else{
					p[i][j].push_back(tot);
				}
			}else{
				if(r<=a[i]) p[i][j].push_back(0);
				else if(r<=b[i]){
					p[i][j].resize(p[i+1][j].size()+1);
					for(int k=0; k<j; k++){
						(p[i][j][0]+=s[k])%=MOD;
					}
					ll pp=l;
					for(int k=0; k<p[i+1][j].size(); k++){
						(p[i][j][0]+=MOD-p[i+1][j][k]*pp%MOD*invs[k+1]%MOD)%=MOD;
						(pp*=l)%=MOD;
						(p[i][j][k+1]+=p[i+1][j][k]*invs[k+1]%MOD)%=MOD;
					}
				}else{
					p[i][j].push_back(tot);
				}
			}
		}
	}
	for(int i=0; i<n; i++){
		(ans*=inv(b[i]-a[i]))%=MOD;
	}
	cout<<ans<<endl;
	return 0;
}