#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000007
ll binpow(ll a, ll b){
ll res = 1;
while (b != 0){
if (b % 2 == 1){
res *= a;
res %= mod;
b--;
}
else{
a *= a;
a %= mod;
b /= 2;
}
}
return res;
}
vector<ll> f, inv;
ll C(int n, int k){
if (k > n || k < 0) return 0;
return f[n] * inv[k] % mod * inv[n - k] % mod;
}
int main(){
f.assign(1001, 1), inv.assign(1001, 1);
for (ll i = 1; i <= 1000; i++){
f[i] = (f[i - 1] * i) % mod;
inv[i] = binpow(f[i], mod - 2);
}
int n;
cin>>n;
vector<int> a(n + 1, 0), b(n + 1, 0);
set<int> se;
for (int i = 1; i <= n; i++){
cin>>a[i]>>b[i];
se.insert(a[i]);
se.insert(b[i]);
}
int m = 0, la = -1;
vector<vector<ll>> ran, pos;
for (auto el : se){
if (la != -1 && la + 1 < el) ran.push_back({la + 1, el - 1});
ran.push_back({el, el});
la = el;
}
m = ran.size();
pos.assign(m, vector<ll>(n + 1, 0));
vector<vector<ll>> c(n + 1, vector<ll>(n + 1, 0));
for (int i = 0; i <= n; i++){
c[i][0] = c[i][i] = 1;
for (int j = 1; j < i; j++){
c[i][j] = (c[i - 1][j] + c[i - 1][j - 1]) % mod;
}
}
for (int i = 0; i < m; i++){
vector<ll> co(n + 1, 0);
ll cur = 1, sz = ran[i][1] - ran[i][0] + 1;
for (int j = 1; j <= n; j++){
cur = (cur * (sz - j + 1)) % mod;
cur = (cur * binpow(j, mod - 2)) % mod;
co[j] = cur;
}
for (int j = 1; j <= n; j++){
for (int k = j; k <= n; k++){
pos[i][k] = (pos[i][k] + c[k - 1][j - 1] * co[j]) % mod;
}
}
}
vector<ll> dp(n + 1, 0);
dp[0] = 1;
for (int wh = 0; wh < m; wh++){
for (int i = n; i >= 1; i--){
if (!(a[i] <= ran[wh][0] && ran[wh][1] <= b[i])) continue;
ll cn = 0;
for (int j = i; j >= 1; j--){
if (a[j] <= ran[wh][0] && ran[wh][1] <= b[j]) cn++;
dp[i] = (dp[i] + dp[j - 1] * pos[wh][cn]) % mod;
}
}
}
ll ans = 0;
for (int i = 1; i <= n; i++){
ans = (ans + dp[i]) % mod;
}
cout<<ans;
}
