#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
int segs[250001],dp[250001];
int length[1001];
int segl[1001];
int l[501],r[501];
int dp2[1001];
int inv[250001];
vector <int> v2[1001];
int p(int a,int b){
int r = 1;
while(b > 0){
if(b%2 == 1)r = 1ll*r*a%mod;
a = 1ll*a*a%mod;
b/=2;
}
return r;
}
void precalc(){
for(int i = 0;i <= 250000;i++){
inv[i] = p(i,mod - 2);
}
}
int main(){
precalc();
int n,i,cnt = 1,j,cnt2 = 0,ans = 0;
cin>>n;
for(i = 0;i < n;i++){
cin>>l[i]>>r[i];
segl[i*2] = l[i];
segl[i*2+1] = r[i] + 1;
}
sort(segl,segl + 2*n);
for(i = 1;i < 2*n;i++){
if(segl[i] != segl[cnt - 1]){
segl[cnt++] = segl[i];
}
}
for(i = 0;i < n;i++){
for(j = cnt - 1;j >= 0;j--){
if(l[i] <= segl[j] && segl[j] <= r[i]){
segs[cnt2++] = j;
length[j] = segl[j + 1] - segl[j];
}
}
}
segs[cnt2++] = cnt;
length[cnt] = 1;
for(i = 0;i < cnt2;i++){
dp[i] = 1;
for(j = segs[i] - 1;j >= 0;j--){
dp[i]+=dp2[j];
dp[i]%=mod;
}
///update dp2[segs[i]]
dp2[segs[i]] = 0;
v2[segs[i]].push_back(dp[i]);
int prod = length[segs[i]];
for(j = v2[segs[i]].size() - 1;j >= 0;j--){
dp2[segs[i]] = (dp2[segs[i]] + 1ll*v2[segs[i]][j]*prod)%mod;
prod = 1ll*prod*(length[segs[i]] + v2[segs[i]].size() - j)%mod;
prod = 1ll*prod*inv[v2[segs[i]].size() - j + 1]%mod;
}
}
ans = (dp[cnt2 - 1] + mod - 1)%mod;
cout<<ans;
return 0;
}
