#include <bits/stdc++.h>
using namespace std;
using namespace chrono;
#define io ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define fi first
#define se second
#define eb emplace_back
#define endl '\n'
#define int long long
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpii;
const int INF = 1e9;
const int mod = 1e9 + 7;
const ll LINF = 1e18;
#define TIMER_START auto start_time = high_resolution_clock::now();
#define TIMER_END auto end_time = high_resolution_clock::now(); \
auto duration = duration_cast<milliseconds>(end_time - start_time).count(); \
cerr << "\nExecution Time: " << duration << " ms\n";
void fname(const string& task_name) {
freopen((task_name + ".inp").c_str(), "r", stdin);
freopen((task_name + ".out").c_str(), "w", stdout);
}
ll power (ll a, ll b) {
if(b == 0) return 1;
ll res = power(a, b / 2);
res = res * res % mod;
if(b & 1) return res * a % mod;
return res;
}
int f[505], inv_f[505], sz[1005], sz1[1005];
void add (int &x, int y) {
x += y;
if(x >= mod) x -= mod;
}
ll mul (int x, int y) {
return (ll)x * y % mod;
}
int dp[2][1005][505], n, a[505], b[505], tot[1005], C[1005][505];
vector<int> comp;
void solve() {
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i] >> b[i];
comp.eb(a[i]);
comp.eb(b[i] + 1);
}
comp.eb(0);
sort(comp.begin(), comp.end());
comp.erase(unique(comp.begin(), comp.end()), comp.end());
int M = comp.size() - 1;
for (int i = 0; i <= M; i++) {
if(i < M) {
sz[i] = min(n, comp[i + 1] - comp[i]);
sz1[i] = comp[i + 1] - comp[i];
}
else {
sz[i] = sz1[i] = 1;
}
}
for (int i = 0; i <= M; i++) {
ll tu = 1, mau = 1;
C[i][0] = 1;
for (int len = 1; len <= sz[i]; len ++) {
tu = tu * (sz1[i] - len + 1) % mod;
mau = mau * len % mod;
C[i][len] = tu * power(mau, mod - 2) % mod;
// cout << C[i][len] << endl;
}
}
dp[0][0][0] = 1;
for (int i = 1; i <= n; i++) {
int cur = i & 1, prv = cur ^ 1;
for (int j = 0; j <= M; ++j) for (int len = 0; len <= sz[j]; ++len) dp[cur][j][len] = 0;
for (int j = 0; j <= M; j++) {
for (int len = 0; len <= sz[j]; len ++) {
add(dp[cur][j][len], dp[prv][j][len]);
}
}
int L = lower_bound(comp.begin(), comp.end(), a[i]) - comp.begin();
int R = lower_bound(comp.begin(), comp.end(), b[i] + 1) - comp.begin() - 1;
if(R < L) {
continue;
}
for (int k = 0; k <= R; ++k) {
if (k > 0) tot[k] = tot[k-1];
else tot[k] = 0;
for (int len = 0; len <= sz[k]; ++len) {
if (dp[prv][k][len] == 0) continue;
add(tot[k], mul(dp[prv][k][len], C[k][len]));
}
}
for (int j = L; j <= R; j++) {
for (int len = 0; len < sz[j]; len ++) {
add(dp[cur][j][len + 1], dp[prv][j][len]);
}
if(j > 0)
add(dp[cur][j][1], tot[j - 1]);
}
}
int ans = 0;
for (int j = 0; j <= M; j++) {
for (int len = 0; len <= sz[j]; len ++) {
add(ans, mul(dp[n & 1][j][len], C[j][len]));
}
}
ans = (ans - 1) % mod;
if (ans < 0) ans += mod;
cout << ans << '\n';
}
int32_t main() {
io;
// fname("task");
TIMER_START;
solve();
TIMER_END;
return 0;
}
