#include <bits/stdc++.h>
using namespace std;
int N;
const long long MOD = 1e9+7;
long long cst[505][1005];
long long dp[505][1005];
long long choose[505][505];
long long temp[505];
int lft[505], rht[505];
vector<int> cmp;
long long add(long long a, long long b){
return (a+b)%MOD;
}
long long mult(long long a, long long b){
return (a*b)%MOD;
}
long long qikpow(long long b, long long e){
if(!e){
return 1;
}
long long ret = qikpow(b, e>>1);
ret = mult(ret, ret);
if(e&1){
ret = mult(ret, b);
}
return ret;
}
long long divd(long long a, long long b){
return mult(a, qikpow(b, MOD-2));
}
int main(){
cin.sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> N;
//cmp.push_back(0);
for(int i= 1; i<=N; i++){
cin >> lft[i] >> rht[i];
cmp.push_back(lft[i]);
cmp.push_back(rht[i]+1);
}
sort(cmp.begin(), cmp.end());
cmp.erase(unique(cmp.begin(), cmp.end()), cmp.end());
const int K = cmp.size()-1;
for(int i = 1; i<=N; i++){
lft[i] = lower_bound(cmp.begin(), cmp.end(), lft[i]) - cmp.begin();
rht[i] = lower_bound(cmp.begin(), cmp.end(), rht[i]+1) - cmp.begin();
}
choose[0][0] = 1;
for(int i = 0; i<=N; i++){
choose[i][0] = 1;
for(int k = 1; k<=N; k++){
choose[i][k] = add(choose[i-1][k], choose[i-1][k-1]);
}
}
temp[0] = 1;
for(int k = 1; k<=K; k++){
for(int n = 1; n<=N; n++){
if(n > cmp[k]-cmp[k-1]){
temp[n] = 0;
}
else{
temp[n] = mult(temp[n-1], cmp[k]-cmp[k-1]-n+1);
temp[n] = divd(temp[n], n);
}
}
for(int n = 1; n<=N; n++){
for(int a = 1; a<=n; a++){
//cout << temp[a] << " " << choose[n-1][a-1] << "\n";
cst[n][k] = add(cst[n][k], mult(choose[n-1][a-1], temp[a]));
}
//cout << n << " " << k << " " << cst[n][k] << "\n";
}
}
for(int k = 0; k<=K; k++){
dp[0][k] = 1;
}
for(int i = 1; i<=N; i++){
for(int k = 1; k<=K; k++){
dp[i][k] = dp[i][k-1];
if(rht[i] >= k && lft[i] < k){
int cnt = 0;
for(int j = i; j; j--){
if(rht[j] >= k && lft[j] < k){
cnt++;
}
dp[i][k] = add(dp[i][k], mult(dp[j-1][k-1], cst[cnt][k]));
}
}
}
}
long long ans = 0;
for(int i = 1; i<=N; i++){
//cout << dp[i][K] << " ";
ans = add(ans, dp[i][K]);
}
cout << ans << "\n";
}
