/***********************************************
* auth: tapilyoca *
* date: 06/29/2025 at 19:58:10 *
* dots: https://github.com/tapilyoca/dotilyoca *
***********************************************/
#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9+7;
template<typename T>
using vec = vector<T>;
using ll = long long;
using vll = vec<ll>;
using vvll = vec<vll>;
using pll = pair<ll,ll>;
using str = string;
#define pb push_back
#define dbg(x) if(1) cerr << #x << ": " << x << endl;
/***********************************************/
ll modpow(ll x, ll y) {
x %= MOD;
ll out = 1;
while(y) {
if(y & 1) out = (out * x) % MOD;
x = (x * x) % MOD;
y >>= 1;
}
return out;
}
ll invert(ll p) {
return modpow(p,MOD-2);
}
void solve() {
ll n;
cin >> n;
vll starts(n+1,0), ends(n+1,0);
set<ll> bounds;
for(int i = 1; i <= n; i++) {
cin >> starts[i] >> ends[i];
starts[i]--; // so relevant[i] - relevant[i-1] is full range always
bounds.insert(starts[i]);
bounds.insert(ends[i]);
}
vll relevant(bounds.begin(),bounds.end());
ll P = relevant.size();
ll N = n;
// precomp range choose inverse thing
// O(n^2)
vvll choose(P+1,vll(N+1,1));
for(int i = 1; i < P; i++) {
choose[i][1] = relevant[i] - relevant[i-1];
choose[i][1] %= MOD;
for(int j = 2; j <= N; j++) {
//comb(n,k) = comb(n,k-1) * (n-k+1)/k
choose[i][j] = (choose[i][j-1] * (choose[i][1] + j - 1) * invert(j)) % MOD;
// cerr << i << " " << j << endl;
}
}
// for(int i = 1; i < P; i++) {
// for(int j = 1; j <= N; j++) {
// cerr << relevant[i] - relevant[i-1] << " choose " << j << " is " << choose[i][j] << endl;
// }
// }
// cerr << "precomp done" << endl;
vvll dp(N+1,vll(P+1,0)); // ans up to i assuming the ith school sends out <= relevant[j]
for(int p = 0; p < P; p++) dp[0][p] = 1;
for(int i = 1; i <= N; i++) {
dp[i][0] = 1; // only possible if nobody has sent out anything
for(int p = 1; p < P; p++) {
dp[i][p] = dp[i][p-1];
ll senders = 0;
for(int k = i-1; k >= 0; k--) {
if(relevant[p] <= starts[k+1] or ends[k+1] < relevant[p]) continue;
// k can send
senders++;
dp[i][p] += dp[k][p-1] * choose[p][senders];
dp[i][p] %= MOD;
}
}
}
// cerr << "dp" << endl;
// for(int i = 0; i <= N; i++) {
// for(int j = 0; j < P; j++) {
// cerr << dp[i][j] << " ";
// } cerr << endl;
// }
cout << (dp[N][P-1]-1 + MOD) % MOD << endl;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
int t = 1;
while(t--) {
solve();
}
return 0;
}
