#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 500;
const int X = 1000;
const ll MOD = 1'000'000'007;
int n, a[N + 10], b[N + 10];
int l[N + 10], r[N + 10], x;
ll c[X + 10][N + 10], dp[2][X + 10][N + 10];
ll fact[N + 10], invFact[N + 10], len[X + 10];
vector<ll> vec;
void readInput() {
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i] >> b[i];
vec.push_back(a[i]);
vec.push_back(b[i] + 1);
}
}
void cmp() {
sort(vec.begin(), vec.end());
vec.resize(unique(vec.begin(), vec.end()) - vec.begin());
for (int i = 1; i <= n; i++) {
l[i] = lower_bound(vec.begin(), vec.end(), a[i]) - vec.begin();
r[i] = lower_bound(vec.begin(), vec.end(), b[i] + 1) - vec.begin();
}
for (int i = 0; i + 1 < vec.size(); i++)
len[i] = vec[i + 1] - vec[i];
x = (int) vec.size() - 2;
}
ll power(ll x, ll k) {
return k? power(x * x % MOD, k >> 1) * ((k & 1)? x: 1) % MOD: 1;
}
void calcFact() {
fact[0] = invFact[0] = 1;
for (int i = 1; i <= n; i++) {
fact[i] = fact[i - 1] * i % MOD;
invFact[i] = power(fact[i], MOD - 2);
}
}
void calcC() {
for (int i = 0; i <= x; i++) {
ll mul = 1;
for (int j = 0; j <= n; j++) {
c[i][j] = mul * invFact[j] % MOD;
mul = mul * (len[i] - j) % MOD;
}
}
}
void clearDP(int t) {
for (int i = 0; i <= x; i++)
for (int j = 0; j <= n; j++)
dp[t][i][j] = 0;
}
void calcDP() {
for (int k = 1; k <= n; k++) {
int last = 1 - k % 2, tmp = k % 2;
clearDP(tmp);
ll sum = 0;
for (int i = 0; i <= x; i++) {
if (l[k] <= i && i < r[k]) {
dp[tmp][i][1] = (sum + 1) % MOD;
for (int j = 1; j < k; j++)
dp[tmp][i][j + 1] = (dp[tmp][i][j + 1] + dp[last][i][j]) % MOD;
}
for (int j = 1; j < k; j++) {
sum = (sum + dp[last][i][j] * (c[i][j] % MOD)) % MOD;
dp[tmp][i][j] = (dp[tmp][i][j] + dp[last][i][j]) % MOD;
}
}
}
}
void calcAns() {
int t = n % 2;
ll ans = 0;
for (int i = 0; i <= x; i++)
for (int j = 1; j <= n; j++)
ans = (ans + dp[t][i][j] * (c[i][j] % MOD)) % MOD;
cout << ans << flush;
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
readInput();
cmp();
calcFact();
calcC();
calcDP();
calcAns();
return 0;
}
