#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9+7;
long long modpow(long long a, long long b) {
long long res = 1;
while (b) {
if (b & 1) res = res * a % MOD;
a = a * a % MOD;
b >>= 1;
}
return res;
}
long long modinv(long long a) { return modpow(a, MOD-2); }
long long C(int n, int k) {
if (k < 0 || k > n) return 0;
static vector<long long> fact(1,1), invfact(1,1);
while ((int)fact.size() <= n) {
fact.push_back(fact.back() * (int)fact.size() % MOD);
invfact.push_back(modinv(fact.back()));
}
return fact[n] * invfact[k] % MOD * invfact[n-k] % MOD;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int N; cin >> N;
vector<long long> A(N+1), B(N+1);
vector<long long> vals;
for (int i=1;i<=N;i++) {
cin >> A[i] >> B[i];
vals.push_back(A[i]);
vals.push_back(B[i]+1);
}
sort(vals.begin(), vals.end());
vals.erase(unique(vals.begin(), vals.end()), vals.end());
int M = vals.size();
vector<vector<long long>> dp(N+1, vector<long long>(M));
vector<vector<long long>> pref(N+1, vector<long long>(M));
for (int i=1;i<=N;i++) {
for (int j=0;j<M-1;j++) {
if (A[i] <= vals[j] && vals[j+1]-1 <= B[i]) {
long long L = vals[j+1]-vals[j];
for (int p=1;p<i;p++) {
dp[i][j] = (dp[i][j] + pref[p][j-1] * C(L+(i-p)-1, i-p)) % MOD;
}
}
}
for (int j=0;j<M;j++) {
pref[i][j] = (dp[i][j] + (j?pref[i][j-1]:0)) % MOD;
}
}
long long ans = 0;
for (int i=1;i<=N;i++) for (int j=0;j<M;j++) ans = (ans + dp[i][j]) % MOD;
cout << ans << "\n";
}
