#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 5e2 + 10, mod = 1e9 + 7;
ll n, a[MAXN], b[MAXN], fact[MAXN], inv[MAXN], I[MAXN];
ll dp[MAXN][MAXN], f[MAXN][MAXN], ps[MAXN][MAXN];
vector<ll> num;
ll findMod(ll a, ll b) {
if (b == 0)
return 1;
ll t = findMod(a, b / 2);
if (b % 2 == 0)
return (t * t) % mod;
return (((t * t) % mod) * a) % mod;
}
ll find(ll a, ll b) {
return (a * findMod(b, mod - 2)) % mod;
}
void calcFact() {
fact[0] = 1;
for (int i = 1; i < MAXN; i++) {
fact[i] = (fact[i - 1] * i) % mod;
I[i] = find(1, i);
}
inv[MAXN - 1] = find(1, fact[MAXN - 1]) % mod;
for (int i = MAXN - 2; i >= 0; i--)
inv[i] = (inv[i + 1] * (i + 1)) % mod;
}
ll crn(ll a, ll b) {
if (b < 0 || (a < 0 || a > b))
return 0;
return (fact[b] * ((inv[a] * inv[b - a]) % mod)) % mod;
}
void input() {
cin >> n;
num.push_back(1);
num.push_back(1e9 + 1);
for (int i = 0; i < n; i++) {
cin >> a[i] >> b[i];
num.push_back(a[i]);
num.push_back(b[i] + 1);
}
sort(num.begin(), num.end());
num.resize(unique(num.begin(), num.end()) - num.begin());
}
bool check(int i, int j) {
return (a[i] <= num[j] && b[i] >= (num[j + 1] - 1));
}
void calcDp() {
for (int j = 0; j < num.size() - 1; j++) {
ll l = num[j + 1] - num[j];
for (int x = 1; x <= n; x++) {
ll comb = 1;
for (int i = 1; i <= x; i++) {
comb = (((comb * (l - i + 1)) % mod) * I[i]) % mod;
f[x][i] = (comb * crn(i - 1, x - 1)) % mod;
ps[x][i] = (ps[x][i - 1] + f[x][i]) % mod;
}
}
for (int i = 0; i < n; i++) {
int cnt = 0;
dp[j][i] = (!j? 1: dp[j - 1][i]);
for (int k = i; k >= 0; k--) {
if (check(k, j))
cnt++;
dp[j][i] = (dp[j][i] + f[cnt][cnt] * ((k == 0 || j == 0)? 1: dp[j - 1][k - 1])) % mod;
}
}
}
}
int main() {
ios::sync_with_stdio(false); cin.tie(0);
calcFact();
input();
calcDp();
cout << (dp[num.size() - 2][n - 1] - 1 + mod) % mod << endl;
return 0;
}
