#include <iostream>
#include<string>
#include<cmath>
#include<map>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<set>
#include<cstdio>
#include<stack>
#include<ctime>
#include<queue>
#include<deque>
#include<bitset>
#include<random>
#include<fstream>
#include<unordered_map>
#include<unordered_set>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using uint = unsigned int;
using dbl = double;
# define all(x) x.begin(), x.end()
# define rall(x) x.rbegin(), x.rend()
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
ll gcd(ll a, ll b) {
return b == 0 ? a : gcd(b, a % b);
}
ll lcm(ll a, ll b) {
return a / gcd(a, b) * b;
}
ll bpow(ll a, ll n) {
return n == 0 ? 1 : n % 2 ? bpow(a, n - 1) * a : bpow(a * a, n / 2);
}
ll bpowm(ll a, ll n, ll m) {
return n == 0 ? 1 : n % 2 ? bpowm(a, n - 1, m) * a % m : bpowm(a * a % m, n / 2, m);
}
mt19937_64 mt(time(0));
const int N = 1e3 + 2, M = 5e5 + 2, inf = 1e9 + 10, mod = 1e9 + 7, mod2 = 998244353, P = 257, htm = 30000001;
const ll llinf = 1e18 + 100;
int add(int a, int b) {
return a + b - mod * (a + b >= mod);
}
ll inv(ll x) {
return bpowm(x, mod - 2, mod);
}
struct fenwick {
int t[M];
fenwick() {
fill(t, t + M, 0);
}
void upd(int i, int x) {
for (++i; i < M; i += (i & -i)) t[i] = add(t[i], x);
}
int get(int r) {
int ans = 0;
for (; r; r -= (r & -r)) ans = add(ans, t[r]);
return ans;
}
};
int n, m = 1;
pair<int, int> a[N];
int b[M];
vector<int> pos[N];
int dp[N][N][2];
void solve() {
cin >> n;
vector<int> vals;
for (int i = 0; i < n; ++i) {
cin >> a[i].first >> a[i].second;
++a[i].second;
vals.push_back(a[i].first);
vals.push_back(a[i].second);
}
sort(all(vals));
vals.erase(unique(all(vals)), vals.end());
for (int i = 0; i < n; ++i) {
int l = lower_bound(all(vals), a[i].first) - vals.begin();
int r = lower_bound(all(vals), a[i].second) - vals.begin() - 1;
for (; r >= l; --r) {
b[m] = r;
pos[r].push_back(m);
++m;
}
}
fenwick t;
t.upd(0, 1);
for (int val = 0; val < vals.size() - 1; ++val) {
int k = pos[val].size();
for (int i = 0; i < k; ++i) {
for (int j = 0; j <= k; ++j) {
dp[i][j][0] = 0;
dp[i][j][1] = 0;
}
}
for (int i = 0; i < k; ++i) {
dp[i][1][1] = t.get(pos[val][i]);
if (i + 1 == k) break;
for (int j = 0; j <= i + 1; ++j) {
dp[i + 1][j][0] = add(dp[i + 1][j][0], add(dp[i][j][0], dp[i][j][1]));
dp[i + 1][j + 1][1] = add(dp[i + 1][j + 1][1], add(dp[i][j][0], dp[i][j][1]));
}
}
int len = vals[val + 1] - vals[val];
ll C = len;
for (int c = 1; c <= min(k, len); ++c) {
for (int i = 0; i < k; ++i) {
t.upd(pos[val][i], dp[i][c][1] * C % mod);
}
C *= (len - c);
C %= mod;
C *= inv(c + 1);
C %= mod;
}
}
cout << (t.get(M - 1) - 1 + mod) % mod;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//freopen("coloring.in", "r", stdin);
//freopen("coloring.out", "w", stdout);
//ld time1 = clock();
int tt = 1;
//cin >> tt;
while (tt--) {
solve();
cout << '\n';
cout.flush();
}
//ld time2 = clock();
//cerr << "\n\nTIME: " << (time2 - time1) / CLOCKS_PER_SEC;
return 0;
}
