#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define sz(v) (int)(v).size()
const int md = (int)1e9 + 7;
const int N = (int)1e5 + 1;
vector<int> fct(N), inv(N), inv_fct(N);
int pw(int x, int y) {
int res = 1;
while (y) {
if (y & 1) res = (ll)res * x % md;
x = (ll)x * x % md; y >>= 1;
}
return res;
}
int C(int n, int r) {
int x = 1;
for (int i = 1; i <= r; i++) x = (ll)x * (n - r + i) % md;
return (ll)x * inv_fct[r] % md;
}
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
fct[0] = inv[0] = inv_fct[0] = 1;
for (int i = 1; i < N; i++) {
inv[i] = pw(i, md - 2);
fct[i] = (ll)fct[i - 1] * i % md;
inv_fct[i] = pw(fct[i], md - 2);
}
int n;
cin >> n;
map<int, vector<int>> m;
vector<int> a(n + 1), b(n + 1);
for (int i = 1; i <= n; i++) {
cin >> a[i] >> b[i];
m[a[i]].push_back(i);
m[b[i] + 1].push_back(-i);
}
vector<int> mv;
for (auto i : m) mv.push_back(i.first);
set<int> s;
vector<int> dp(n + 1);
for (int ii = 0; ii + 1 < sz(mv); ii++) {
for (auto j : m[mv[ii]]) {
if (0 < j) s.insert(j);
else s.erase(-j);
}
int R = mv[ii + 1] - mv[ii];
vector<int> v(s.begin(), s.end()), nw_dp = dp;
for (int i = 0; i < sz(v); i++) {
int sm = 1;
for (int j = 1; j < v[i]; j++) sm = (sm + dp[j]) % md;
nw_dp[v[i]] = (dp[v[i]] + (ll)sm * R % md) % md;
vector<int> p(n);
for (int j = 0; j < n; j++) p[j] = ((j ? p[j - 1] : 0) + dp[j]) % md;
for (int j = 1; j <= min(i, R - 1); j++) {
int c = C(R, j + 1), x = fct[j - 1];
// cout << "\nj " << j << ' ' << x << '\n';
for (int k = i - j; k >= 0; k--) {
int pre = ((v[k] ? p[v[k] - 1] : 0) + 1) % md;
if (k != i - j) x = (ll)x * (i - k - 1) * inv[i - k - j] % md;
nw_dp[v[i]] = (nw_dp[v[i]] + ((ll)pre * ((ll)x * inv_fct[j - 1] % md) % md) * c % md) % md;
// cout << i - k - 1 << ' ' << j - 1 << ' ' << x << ' ' << (ll)x * inv_fct[j - 1] % md << ' ' << C(i - k - 1, j - 1) << '\n';
}
}
}
dp = nw_dp;
}
int sm = 0;
for (auto i : dp) sm = (sm + i) % md;
cout << sm << '\n';
}
