#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 505;
const ll mod = 1e9 + 7;
int n;
// 區間（已離散）
pair<int,int> seg[N];
// 座標壓縮
vector<int> xs;
// 每一小段長度
int lenv[N * 2];
// DP
ll f[N][N * 2];
// 逆元
ll inv[N + 5];
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
xs.push_back(0);
// 讀入 + 收集座標
for (int i = 1; i <= n; i++) {
int l, r;
cin >> l >> r;
r++; // 轉成 [l, r)
seg[i] = {l, r};
xs.push_back(l);
xs.push_back(r);
}
// 離散化
sort(xs.begin() + 1, xs.end());
xs.erase(unique(xs.begin() + 1, xs.end()), xs.end());
int m = (int)xs.size() - 1;
// 區間轉 index
for (int i = 1; i <= n; i++) {
seg[i].first = lower_bound(xs.begin() + 1, xs.end(), seg[i].first) - xs.begin();
seg[i].second = lower_bound(xs.begin() + 1, xs.end(), seg[i].second) - xs.begin();
}
// 每段長度
for (int i = 1; i < m; i++) {
lenv[i] = xs[i + 1] - xs[i];
}
// 逆元（用來做 /）
inv[1] = 1;
for (int i = 2; i <= n; i++) {
inv[i] = (mod - mod / i) * inv[mod % i] % mod;
}
// base case
for (int j = 0; j <= m; j++) f[0][j] = 1;
// DP
for (int i = 1; i <= n; i++) {
for (int j = seg[i].first; j < seg[i].second; j++) {
ll C = lenv[j]; // C(r,c)
int r = lenv[j];
int c = 1;
for (int k = i - 1; k >= 0; k--) {
// 不選 k（或結束於 k）
f[i][j] = (f[i][j] + f[k][j - 1] * C) % mod;
// 如果 k 也覆蓋這段 → 加入集合
if (k > 0 && seg[k].first <= j && j < seg[k].second) {
r++;
c++;
C = C * r % mod * inv[c] % mod;
}
}
}
// prefix max（保留最佳）
for (int j = 1; j < m; j++) {
f[i][j] = (f[i][j] + f[i][j - 1]) % mod;
}
}
ll ans = 0;
for (int i = 1; i <= n; i++) {
ans = (ans + f[i][m - 1]) % mod;
}
cout << ans << "\n";
}
