#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
int N;
cin >> N;
vector<int> X = {0};
vector<int> A(N + 1), B(N + 1);
for (int i = 1; i <= N; i++) {
cin >> A[i] >> B[i];
X.emplace_back(A[i]);
X.emplace_back(B[i] + 1);
}
sort(begin(X), end(X));
X.erase(unique(begin(X), end(X)), end(X));
for (int i = 1; i <= N; i++) {
A[i] = lower_bound(begin(X), end(X), A[i]) - begin(X);
B[i] = upper_bound(begin(X), end(X), B[i]) - begin(X);
}
const int MOD = 1e9 + 7;
vector<int> inv(N + 1);
inv[0] = 0, inv[1] = 1;
for (int i = 2; i <= N; i++) {
inv[i] = (MOD - 1ll * (MOD / i) * inv[MOD % i] % MOD) % MOD;
}
vector<vector<int>> cmb(N + 1, vector<int>(X.size(), 0));
for (int i = 1; i < (int) X.size(); i++) {
cmb[0][i] = 1;
int x = X[i] - X[i - 1];
for (int j = 1; j <= N; j++) {
cmb[j][i] = 1ll * cmb[j - 1][i] * (x + j - 1) % MOD * inv[j] % MOD;
}
}
vector<vector<int>> dp(N + 1, vector<int>(X.size(), 0));
dp[0] = vector<int>(X.size(), 1);
for (int i = 1; i <= N; i++) {
dp[i][0] = 1;
for (int j = 1; j < (int) X.size(); j++) { // [X[j - 1], X[j])
dp[i][j] = dp[i][j - 1];
for (int k = i, cnt = 0; k > 0; k--) if (A[k] < j && j <= B[k]) {
dp[i][j] += 1ll * cmb[++cnt][j] * dp[k - 1][j - 1] % MOD;
if (dp[i][j] >= MOD) dp[i][j] -= MOD;
}
}
}
cout << ((dp[N][(int) X.size() - 1] - 1 + MOD) % MOD) << "\n";
return 0;
}
