#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define SZ(x) (int) x.size()
const int mod = 1e9 + 7;
struct mint {
int v;
mint(long long x) {
if (x >= mod) x %= mod;
v = x;
}
mint() {v = 0;}
mint& operator+=(mint b) {
if ((v += b.v) >= mod) {
v -= mod;
}
return *this;
}
mint& operator-=(mint b) {
if ((v -= b.v) < 0) {
v += mod;
}
return *this;
}
mint& operator*=(mint b) {
v = 1ll * v * b.v % mod;
return *this;
}
mint power(mint a, int b) {
mint ans = 1;
while (b) {
if (b & 1) {
ans *= a;
}
a *= a, b >>= 1;
}
return ans;
}
mint& operator/=(mint b) {
v = 1ll * v * power(b, mod - 2).v % mod;
return *this;
}
friend mint operator+(mint a, mint b) {
return a += b;
}
friend mint operator-(mint a, mint b) {
return a -= b;
}
friend mint operator*(mint a, mint b) {
return a *= b;
}
friend mint operator/(mint a, mint b) {
return a /= b;
}
friend istream& operator>>(istream &is, mint &a) {
return is >> a.v;
}
friend ostream& operator<<(ostream &os, mint a) {
return os << a.v;
}
};
const int N = 505;
mint fact[N], inv[N];
mint nCr(int n, int r) {
if (n < 0 || r < 0 || n - r < 0) return 0;
// cout << "> " << n << ' ' << r << ' ' << fact[n] * inv[r] * inv[n - r] << '\n';
return fact[n] * inv[r] * inv[n - r];
}
int main() {
ios_base::sync_with_stdio(0), cin.tie(0);
fact[0] = 1;
for (int i = 1; i < N; i++) {
fact[i] = fact[i - 1] * i;
}
inv[N - 1] = 1 / fact[N - 1];
for (int i = N - 2; i >= 0; i--) {
inv[i] = inv[i + 1] * (i + 1);
}
int n;
cin >> n;
array<int, 2> a[n];
vector<int> v;
for (int i = 0; i < n; i++) {
cin >> a[i][0] >> a[i][1];
v.push_back(a[i][0]);
v.push_back(a[i][1]);
v.push_back(a[i][1] + 1);
}
sort(v.begin(), v.end());
v.resize(unique(v.begin(), v.end()) - v.begin());
auto get = [&] (int x) {
return lower_bound(v.begin(), v.end(), x) - v.begin();
};
int m = v.size();
vector<int> gud[m];
for (int i = 0; i < n; i++) {
int l = get(a[i][0]), r = get(a[i][1]);
for (int j = l; j <= r; j++) {
gud[j].push_back(i + 1);
}
}
mint dp[m + 1][n + 1];
for (int j = 1; j <= n; j++) {
dp[m][j] = 1;
}
for (int i = m - 1; i >= 0; i--) {
int sz = gud[i].size();
mint dp2[sz + 1][sz + 1];
for (int j = sz - 1; j >= 0; j--) {
for (int k = 1; k <= sz; k++) {
dp2[j][k] += dp2[j + 1][k];
if (k == 1) {
dp2[j][k] += dp[i + 1][gud[i][j]];
} else {
dp2[j][k] += dp2[j + 1][k - 1];
}
}
}
for (int j = 0; j <= n; j++) {
int pos = SZ(gud[i]);
for (int k = 0; k < SZ(gud[i]); k++) {
if (j < gud[i][k]) {
pos = k;
break;
}
}
dp[i][j] = dp[i + 1][j];
for (int k = 1; k <= SZ(gud[i]) - pos; k++) {
// cout << k << ' ' << dp2[pos][k] << ' ' << v[i + 1] - v[i] << ' ' << k << ' ' << nCr(v[i + 1] - v[i], k) << '\n';
dp[i][j] += dp2[pos][k] * nCr(v[i + 1] - v[i], k);
}
}
}
// for (int i = 0; i < m; i++) {
// for (int j = 0; j <= n; j++) {
// cout << dp[i][j] << ' ';
// }
// cout << '\n';
// }
cout << dp[0][0] << '\n';
return 0;
}
