#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define sp <<" "<<
#define endl "\n"
const ll MOD = 1e9+7;
const int MAXK = 1e3+5;
vector<int> feli;
ll inv[MAXK];
ll binpow(ll a, ll b) {
ll res = 1;
while (b) {
if (b & 1) res = (res * a) % MOD;
a = (a * a) % MOD;
b >>= 1;
}
return res;
}
int o(int x) {
return lower_bound(feli.begin(), feli.end(), x) - feli.begin();
}
void gen() {
inv[0] = 0;
for (int i = 1; i < MAXK; i++) {
inv[i] = binpow(i, MOD-2);
}
}
void solve() {
int n; cin >> n;
vector<int> l(n+1), r(n+1);
for (int i = 1; i <= n; i++) {
cin >> l[i] >> r[i];
feli.push_back(--l[i]);
feli.push_back(r[i]);
}
sort(feli.begin(), feli.end());
feli.erase(unique(feli.begin(), feli.end()), feli.end());
for (int i = 1; i <= n; i++) {
l[i] = o(l[i]);
r[i] = o(r[i]);
}
int m = feli.size();
vector<vector<ll>> dp(n+1, vector<ll>(m, 0));
dp[0][0] = 1;
for (int j = 1; j < m; j++) {
dp[0][j] = 1;
for (int i = 1; i <= n; i++) {
dp[i][j] = dp[i][j-1];
ll cnt = 1, eff = feli[j] - feli[j-1];
if (!(l[i] < j and j <= r[i])) continue;
for (int k = i-1; k >= 0; k--) {
dp[i][j] = (dp[i][j] + ((dp[k][j-1] * eff) % MOD)) % MOD;
if (l[k] < j and j <= r[k]) {
eff = (((eff * (cnt + feli[j] - feli[j-1])) % MOD) * inv[cnt+1]) % MOD;
cnt++;
}
}
}
}
ll ans = 0;
for (int i = 1; i <= n; i++) ans = (ans + dp[i][m-1]) % MOD;
cout << ans << endl;
}
signed main() {
cin.tie(0);
ios_base::sync_with_stdio(false);
gen();
int t = 1;
// cin >> t;
while (t--)
solve();
}
