#include<iostream>
#include<algorithm>
#include<vector>
#include<unordered_map>
using namespace std;
typedef long long ll;
#define chmin(a,b) a=min(a,b)
#define chmax(a,b) a=max(a,b)
#define all(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<n;i++)
#define mod 1000000007
#define mad(a,b) a=(a+b)%mod
#define mul(a,b) a=a*b%mod
#define N 510
ll po(ll x,ll y){
ll res=1;
for(;y;y>>=1){
if(y&1)mul(res,x);
x=x*x%mod;
}
return res;
}
ll inv[N];
unordered_map<ll,ll> C[N];
void calcc(ll l){
ll res=1;
for(int i=1;i<N;i++){
mul(res,l);
mul(res,inv[i]);
if(i>l)res=0;
C[i][l]=res;
}
}
unordered_map<ll,ll> f[N];
void initf(ll l){
ll res=0;
for(int i=1;i<N;i++){
mad(res,C[i][l]);
f[i][l]=res;
}
}
ll n,a[N],b[N];
ll rui[2*N][N];
vector<ll> xs;
ll edge(ll j,ll i,ll ii){
ll m=rui[j][ii]-rui[j][i];
/*for(int k=i;k<ii;k++){
if(a[k]<=j&&j<b[k])m++;
}*/
//cout<<"edge("<<j<<","<<i<<","<<ii<<")="<<f(xs[j+1]-xs[j],m)<<endl;
//cout<<"l="<<xs[j+1]-xs[j]<<", m="<<m<<endl;
return f[m][xs[j+1]-xs[j]];
}
ll dp[N][2*N];
int main(){
for(int i=1;i<N;i++)inv[i]=po(i,mod-2);
cin>>n;
a[0]=b[0]=0;
xs.push_back(0); xs.push_back(1);
for(int i=1;i<=n;i++){
cin>>a[i]>>b[i];
}
a[n+1]=2e9,b[n+1]=2e9;
for(int i=0;i<=n+1;i++){
b[i]++;
xs.push_back(a[i]);
xs.push_back(b[i]);
}
sort(all(xs));
xs.erase(unique(all(xs)),xs.end());
for(int i=0;i<=n+1;i++){
a[i]=lower_bound(all(xs),a[i])-xs.begin();
b[i]=lower_bound(all(xs),b[i])-xs.begin();
}
for(int i=0;i<xs.size()-1;i++){
calcc(xs[i+1]-xs[i]);
initf(xs[i+1]-xs[i]);
}
rep(j,xs.size()-1){
rui[j][0]=0;
for(int i=0;i<=n+1;i++){
rui[j][i+1]=rui[j][i]+(a[i]<=j&&j<b[i]);
}
}
for(int i=0;i<=n+1;i++)rep(j,xs.size()-1)dp[i][j]=0;
dp[0][0]=1;
for(int ii=1;ii<=n+1;ii++){
for(int jj=a[ii];jj<b[ii];jj++){
for(int i=0;i<ii;i++)for(int j=0;j<jj;j++){
mad(dp[ii][jj],dp[i][j]*edge(j,i,ii));
}
}
}
ll ans=dp[n+1][a[n+1]]+mod-1; ans%=mod;
cout<<ans<<endl;
}
