// EXPLOSION!
#define _CRT_SECURE_NO_WARNINGS
#include<bits/stdc++.h>
#include<unordered_set>
#include<unordered_map>
#include<chrono>
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pair<int, int>> vpi;
typedef vector<pair<ll, ll>> vpll;
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)
#define pb push_back
#define mp make_pair
#define rsz resize
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define f first
#define s second
#define cont continue
//#define endl '\n'
//#define ednl '\n'
#define test int testc;cin>>testc;while(testc--)
#define pr(a, b) trav(x,a)cerr << x << b; cerr << endl;
#define message cout << "Hello World" << endl;
//const int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 }; // for every grid problem!!
const ll linf = 4000000000000000000LL;
const ll inf = 1000000007;//998244353
void pv(vi a) { trav(x, a)cout << x << " "; cout << endl; }void pv(vll a) { trav(x, a)cout << x << " "; cout << endl; }void pv(vector<vi>a) {
F0R(i, sz(a)) { cout << i << endl; pv(a[i]); cout << endl; }
}void pv(vector<vll>a) { F0R(i, sz(a)) { cout << i << endl; pv(a[i]); }cout << endl; }void pv(vector<string>a) { trav(x, a)cout << x << endl; cout << endl; }
void setIO(string s) {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef arwaeystoamneg
if (sz(s))
{
freopen((s + ".in").c_str(), "r", stdin);
if (s != "test1")
freopen((s + ".out").c_str(), "w", stdout);
}
#endif
}
template<int MOD, int RT> struct mint {
static const int mod = MOD;
static constexpr mint rt() { return RT; } // primitive root for FFT
int v; explicit operator int() const { return v; } // explicit -> don't silently convert to int
mint() { v = 0; }
mint(ll _v) {
v = int((-MOD < _v&& _v < MOD) ? _v : _v % MOD);
if (v < 0) v += MOD;
}
friend bool operator==(const mint& a, const mint& b) {
return a.v == b.v;
}
friend bool operator!=(const mint& a, const mint& b) {
return !(a == b);
}
friend bool operator<(const mint& a, const mint& b) {
return a.v < b.v;
}
mint& operator+=(const mint& m) {
if ((v += m.v) >= MOD) v -= MOD;
return *this;
}
mint& operator-=(const mint& m) {
if ((v -= m.v) < 0) v += MOD;
return *this;
}
mint& operator*=(const mint& m) {
v = int((ll)v * m.v % MOD); return *this;
}
mint& operator/=(const mint& m) { return (*this) *= inv(m); }
friend mint power(mint a, ll p) {// MAKE SURE YOU ARE USING THE CORRECT VERSION OF POW!!!!!!!!
mint ans = 1; assert(p >= 0);
for (; p; p /= 2, a *= a) if (p & 1) ans *= a;
return ans;
}
friend mint inv(const mint& a) {
assert(a.v != 0);
return power(a, MOD - 2);
}
mint operator-() const { return mint(-v); }
mint& operator++() { return *this += 1; }
mint& operator--() { return *this -= 1; }
friend mint operator+(mint a, const mint& b) { return a += b; }
friend mint operator-(mint a, const mint& b) { return a -= b; }
friend mint operator*(mint a, const mint& b) { return a *= b; }
friend mint operator/(mint a, const mint& b) { return a /= b; }
};
typedef mint<inf, 5> mi; // 5 is primitive root for both common mods
typedef vector<mi> vmi;
int n;
vpi a;
vi order, sizes;
vpi b;
vmi fac, ifac;
vector<vmi>c;
mi choose(int x, int y)
{
mi ans = 0, d = x;
F0R(i, y)
{
if (i > x - 1)break;
ans += d * fac[y - 1] * ifac[i] * ifac[i + 1] * ifac[y - i - 1];
d *= (x - i - 1);
}
return ans;
}
int main()
{
setIO("test1");
cin >> n;
ifac.rsz(n + 1);
fac.rsz(n + 1);
fac[0] = 1;
F0R(i, n)
{
fac[i + 1] = (fac[i] * (i + 1));
}
F0R(i, n + 1)ifac[i] = inv(fac[i]);
a.rsz(n);
trav(x, a)cin >> x.f >> x.s, order.pb(x.f), order.pb(x.s);
sort(all(order));
vi temp;
F0R(i, sz(order))
{
if (!sz(temp) || temp.back() != order[i])temp.pb(order[i]);
}
order = temp;
F0R(i, sz(order))
{
sizes.pb(1);
if (i < sz(order) - 1)sizes.pb(order[i + 1] - order[i] - 1);
}
b.rsz(n);
F0R(i, n)
{
b[i].f = 2 * (lower_bound(all(order), a[i].f) - order.begin());
b[i].s = 2 * (lower_bound(all(order), a[i].s) - order.begin());
}
vector<vmi>dp(n + 1, vmi(2 * sz(order)));
F0R(i, n)dp[i][0] = 1;
c.rsz(sz(sizes), vmi(n + 1, -1));
F0R(i, n)
{
F0R(j, 2 * sz(order) - 1)
{
dp[i][j + 1] += dp[i][j];
if (sizes[j] && b[i].f <= j && j <= b[i].s)
{
int co = 0;
FOR(k, i + 1, n + 1)
{
if (b[k - 1].f <= j && j <= b[k - 1].s)co++;
if (co)
{
mi c1 = c[j][co];
if (c1 == -1)
{
c1 = choose(sizes[j], co);
c[j][co] = c1;
}
dp[k][j + 1] += dp[i][j] * c1;
}
}
}
}
}/*
F0R(i, n + 1)
{
F0R(j, 2 * sz(order))
{
cerr << (int)dp[i][j] << " ";
}
cerr << endl;
}*/
mi ans = 0;
F0R(i, 2 * sz(order))ans += dp[n][i];
cout << (int)ans << endl;
}
