#include <bits/stdc++.h>
using namespace std;
#define rep(i, s, t) for (int i = s; i < t; i++)
#define per(i, s, t) for (int i = s; i >= t; i--)
#define sz(x) ((int)x.size())
#define all(x) (x).begin(), (x).end()
typedef long long ll;
typedef long double ld;
const int INF = (int) (1e9 + 1e6 + 123);
template<typename A, typename B> bool mini(A& x, const B& y) {
if (y < x) {
x = y;
return true;
}
return false;
}
template<typename A, typename B> bool maxi(A& x, const B& y) {
if (y > x) {
x = y;
return true;
}
return false;
}
void run();
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
run();
return 0;
}
const int N = 505;
const int MOD = 1000000000 + 7;
const long long MOD2 = MOD * 1LL * MOD;
void add(int& x, int y) {
x += y;
if (x >= MOD) {
x -= MOD;
}
}
int power(int x, int y) {
if (y == 0) {
return 1;
}
if (y % 2 == 0) {
return power(x * 1LL * x % MOD, y / 2);
} else {
return power(x, y - 1) * 1LL * x % MOD;
}
}
int n;
int a[N], b[N];
vector<int> cool;
int fact[N];
int rfact[N];
int dp[2 * N][N];
int nxt[2 * N][N];
int prec[2 * N][N];
int cnk(int n, int k) {
if (k > n) {
return 0;
}
int res = 1;
rep(i, 0, k) {
res = res * 1LL * (n - i) % MOD;
}
res = res * 1LL * rfact[k] % MOD;
return res;
}
void upd(int l, int r) {
memcpy(nxt, dp, sizeof dp);
long long pref = 0;
rep(block, 0, sz(cool)) {
int len = cool[block + 1] - cool[block];
if (l <= block && block <= r) {
add(nxt[block][1], pref % MOD);
}
rep(cnt, 0, N) {
pref += dp[block][cnt] * 1LL * prec[block][cnt];
if (pref >= MOD2) {
pref -= MOD2;
}
}
pref %= MOD;
}
rep(block, 0, sz(cool)) {
if (l <= block && block <= r) {
rep(cnt, 2, N) {
add(nxt[block][cnt], dp[block][cnt - 1]);
}
}
}
swap(nxt, dp);
}
void run() {
cin >> n;
rep(i, 0, n) {
cin >> a[i] >> b[i];
cool.push_back(a[i]);
cool.push_back(b[i] + 1);
}
cool.push_back(0);
sort(all(cool));
cool.resize(unique(all(cool)) - cool.begin());
cool.push_back(INF);
fact[0] = 1;
rep(i, 1, N) {
fact[i] = fact[i - 1] * 1LL * i % MOD;
}
rep(i, 0, N) {
rfact[i] = power(fact[i], MOD - 2);
}
rep(i, 0, sz(cool) - 1) {
int len = cool[i + 1] - cool[i];
rep(j, 0, N) {
prec[i][j] = cnk(len, j);
}
}
dp[0][0] = 1;
rep(i, 0, n) {
int l = 0;
while (cool[l] != a[i]) {
l++;
}
int r = l;
while (cool[r + 1] <= b[i]) {
r++;
}
upd(l, r);
}
int ans = MOD - 1;
rep(i, 0, sz(cool) - 1) {
rep(j, 0, N) {
add(ans, dp[i][j] * 1LL * prec[i][j] % MOD);
}
}
cout << ans << "\n";
}
