#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pb push_back
#define all(x) begin(x), end(x)
#define SZ(x) (int)(x).size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int n0 = 1003, mod = 1e9 + 7;
int n, l[n0], r[n0], k, inv[n0];
void add(unsigned int & x, int y) {
x += y;
if (x >= mod) x -= mod;
}
int bp(int x, int y) {
int res = 1;
while (y) {
if (y & 1)
res = (ll)res * x % mod;
x = (ll)x * x % mod;
y /= 2;
}
return res;
}
struct Block {
int l = 0, r = 0, t = 0;
unsigned int val[n0], c[n0], cur = 0, last = 0;
Block() {
c[0] = 1;
}
void upd(int x) {
val[t++] = x;
c[t] = ((ll)c[t - 1] * (r - l + t) % mod) * inv[t] % mod;
cur = last = 0;
for (int i = 0; i < t; i++) {
add(cur, (ll)c[t - i] * val[i] % mod);
add(last, (ll)c[t - i - 1] * val[i] % mod);
}
}
};
Block b[n0];
int main() {
ios_base::sync_with_stdio(false), cin.tie(NULL);
for (int i = 1; i < n0; i++)
inv[i] = bp(i, mod - 2);
cin >> n;
vector <int> crd;
for (int i = 0; i < n; i++) {
cin >> l[i] >> r[i];
r[i]++;
crd.pb(l[i]), crd.pb(r[i]);
}
crd.pb(0), crd.pb(1);
sort(all(crd));
for (int i = 1; i < SZ(crd); i++) {
if (crd[i - 1] < crd[i]) {
b[k].l = crd[i - 1];
b[k++].r = crd[i] - 1;
}
}
b[0].upd(1);
for (int i = 0; i < n; i++) {
unsigned int cur = 0;
int j = 0;
for (; j < k && b[j].r < l[i]; j++)
add(cur, b[j].cur);
for (; j < k && b[j].r < r[i]; j++) {
b[j].upd(cur);
cur = b[j].last;
}
}
unsigned int res = 0;
for (int i = 0; i < k; i++)
add(res, b[i].cur);
add(res, mod - 1);
cout << res;
}
