#include <bits/stdc++.h>
//#define int long long
#define pii pair<int, int>
#define fi first
#define se second
#define vi vector <int>
#define pq priority_queue
#define MASK(i) (1ll<<(i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define x0 ___x0
#define y0 ___y0
#define div ___div
#define next ___next
#define prev ___prev
#define left ___left
#define right ___right
#define pos pisosi
#define pb push_back
#define pf push_front
using namespace std;
const int mod = 1e9+7;
void add (int &a, const int&b){
a+=b;
if (a>=mod) a-=mod;
}
void sub (int&a, const int&b){
a-=b;
if (a<0) a+=mod;
}
void mul (int&a, const int&b){
a = 1ll*a*b%mod;
}
template<class X, class Y>
bool minimize(X &x, const Y&y){
if (x<=y) return false;
else{
x = y;
return true;
}
}
template<class X, class Y>
bool maximize (X &x, const Y&y){
if (x>=y) return false;
else{
x = y;
return true;
}
}
/////////////////////////////////////////////////////////////////////////////////
//// dang nhap ham
//#ifndef davele
//
//#endif // davele
//
//// chay thu ham main:
//
//#ifdef davele
//
//#endif // davele
////////////////////////////////////////////////////////////////////////////
//const int lim = , limit = , inf = ;
const string name = "boat";
const int lim = 1050, limit = lim+5;
int powe (int coso, int somu){
int ret = 1;
while (somu>0){
if (somu&1) mul (ret, coso);
mul (coso, coso);
somu>>=1;
}
return ret;
}
vector <int> ds;
int L[limit], R[limit], numrange;
int sum[limit][limit];
vector <int> inside[limit];
int dp[limit][limit];
int sumdp[limit][limit];
int prep[limit][limit];
int n;
int inv[limit];
int C[limit][limit];
void compress(){
ds.pb(-1);
for (int i=1; i<=n; i++){
ds.pb(L[i]);
ds.pb(R[i]+1);
}
sort (ds.begin(), ds.end());
ds.erase (unique(ds.begin(), ds.end()), ds.end());
ds.pb(ds.back()+1);
// range[i] = [ds[i]; ds[i+1]-1]
//
numrange = ds.size()-2;
// for (int i=1; i<=numrange; i++) cerr<<ds[i]<<" "<<ds[i+1]<<"\n";
}
void process(){
compress();
//
for (int i=1; i<=n; i++){
for (int j=1; j<=numrange; j++){
sum[i][j] = sum[i-1][j];
// cerr<<L[i]<<" "<<R[i]<<" "<<" "<<j<<"\n";
if (L[i]<=ds[j] && ds[j+1]-1<=R[i]){
inside[i].pb(j);
// cerr<<i<<" "<<j<<"\n";
sum[i][j]++;
}
}
}
// sum[i][j] : xet den nguoi thu i, co bao nhieu team co the nam trong range j
// C[k][n]
for (int i=0; i<=lim; i++) C[0][i] = 1;
for (int i=1; i<=lim; i++) for (int j=1; j<=i; j++){
C[j][i] = (C[j-1][i-1] + C[j][i-1])%mod;
}
for (int i=1; i<=lim; i++) inv[i] = powe (i, mod-2);
// prep[kind][cnt] : so cach chon phu hop sao cho voi cnt team thi team cuoi cung chac chan
// duoc chon
// prep[kind][cnt] = sum (C(k-1, cnt-1)*C(k, lenrange)) voi k chay tu 1 den min(cnt, lenrange)
for (int kind = 1; kind<=numrange; kind++){
int lenrange = ds[kind+1]-ds[kind];
for (int cnt = 1; cnt<=sum[n][kind]; cnt++){
int mx = min(cnt, lenrange);
int tu = 1, mau = 1;
for (int chose = 1; chose<=mx; chose++){
mul (tu, lenrange-chose+1);
mul (mau, inv[chose]);
add (prep[kind][cnt], 1ll*C[chose-1][cnt-1]*tu%mod*mau%mod);
}
// cerr<<kind<<" "<<cnt<<" "<<prep[kind][cnt]<<"\n";
}
}
// dp[i][j] : den vi tri i, so cach chon sao cho o group i co chon nguoi o range j
int ret = 0;
dp[0][0] = 1;
for (int i=0; i<=lim; i++) sumdp[0][i] = 1;
for (int i=1; i<=n; i++){
for (int x:inside[i]){
for (int j=0; j<i; j++){
add (dp[i][x], 1ll*sumdp[j][x-1]*prep[x][sum[i][x]-sum[j][x]]%mod);
}
add (ret, dp[i][x]);
}
for (int j=1; j<=numrange; j++) sumdp[i][j] = (sumdp[i][j-1]+dp[i][j])%mod;
}
cout<<ret;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//
if (fopen((name+".inp").c_str(), "r")){
freopen ((name+".inp").c_str(), "r", stdin);
freopen ((name+".out").c_str(), "w", stdout);
}
//
cin>>n;
for (int i=1; i<=n; i++){
cin>>L[i]>>R[i];
}
process();
}
