#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <queue>
using namespace std;
#define all(a) (a).begin(), (a).end()
#define ll long long
#define ld long double
#define ui uint64_t
#define cont(set, element) ((set).find(element) != (set).end())
#define chmin(x, y) (x = min(x, y))
#define chmax(x, y) (x = max(x, y))
/********* DEBUG *********/
template <typename T>
void outvec(const vector<T>& Z){
for (const T& x : Z)
cout << x << ' ';
cout << "\n";
}
void printVariable(const any& var) {
if (!var.has_value()) {
cout << "null";
return;
}
if (var.type() == typeid(int)) {
cout << any_cast<int>(var);
} else if (var.type() == typeid(double)) {
cout << any_cast<double>(var);
} else if (var.type() == typeid(float)) {
cout << any_cast<float>(var);
} else if (var.type() == typeid(char)) {
cout << any_cast<char>(var);
} else if (var.type() == typeid(bool)) {
cout << (any_cast<bool>(var) ? "true" : "false");
} else if (var.type() == typeid(string)) {
cout << any_cast<string>(var);
} else if (var.type() == typeid(const char*)) {
cout << any_cast<const char*>(var);
} else if (var.type() == typeid(long long)) {
cout << any_cast<long long>(var);
} else {
cout << "[unknown type]";
}
}
template<typename... Args>
void outval(Args... args) {
vector<any> variables = {args...};
for (size_t i = 0; i < variables.size(); ++i) {
printVariable(variables[i]);
if (i != variables.size() - 1) {
cout << " ";
}
}
cout << "\n";
}
#define sp << " " <<
#define fi first
#define se second
/********* DEBUG *********/
const ll MOD = 1e9+7;
const ll MOD2 = 998244353;
const ll inf = 1e18;
const ll mxN = 100005;
ll binpow(ll a, ll b, ll m){
a %= m;
ll ans = 1;
while (b){
if (b & 1)
ans = (ans * a) % m;
a = (a * a) % m;
b >>= 1;
}
return ans;
}
ll modinv(ll a, ll m){
return binpow(a, m-2, m);
}
void solve(){
ll n;
cin >> n;
vector<ll> vec, l(n), r(n);
for (int i = 0; i < n; i++){
cin >> l[i] >> r[i];
l[i]--;
vec.push_back(l[i]);
vec.push_back(r[i]);
}
sort(all(vec));
vec.resize(unique(all(vec))-vec.begin());
vector<vector<ll>> c(vec.size()+5, vector<ll>(n+5));
for (int i = 1; i < vec.size(); i++){
c[i][1] = vec[i] - vec[i-1];
for (int j = 2; j <= n; j++){
c[i][j] = ((c[i][j-1] * (vec[i] - vec[i-1] + j - 1) % MOD ) * modinv(j, MOD)) % MOD;
}
}
// dp[i][j] = number of ways using first i schools, such that number of boats sent <= vec[j]
vector<vector<ll>> dp(n+5, vector<ll>(vec.size()+5));
for (int i = 0; i < vec.size(); i++){
dp[0][i] = 1;
}
for (int i = 1; i <= n; i++){
dp[i][0] = 1;
for (int j = 1; j < vec.size(); j++){
dp[i][j] = dp[i][j-1];
ll take = 1;
for (int k = i; k; k--){
if (l[k-1] < vec[j] && vec[j] <= r[k-1]){
dp[i][j] = (dp[i][j] + dp[k-1][j-1] * c[j][take]) % MOD;
take++;
}
}
//outval("i,j,dp[i][j]:",i,j,dp[i][j]);
dp[i][j] %= MOD;
}
}
outval(dp[n][vec.size()-1]-1);
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
ll t = 1;
//cin >> t;
while (t--) {
solve();
}
}
