#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, n) for(int (i) = (a); (i) < (n); ++(i))
#define per(i, n, a) for(int (i) = (n) - 1; (i) >= (a); --(i))
#define trav(i, x) for(auto& (i) : (x))
#define all(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define pb push_back
#define mp make_pair
#define X first
#define Y second
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef double db;
mt19937 mrand(random_device{}());
const int INF = 0x3f3f3f3f;
const int OFF = 1 << 20;
const int MOD = (int)1e9 + 7;
const int N = 550;
int n;
pii q[N];
vector<int> comp;
ll dist[2 * N];
ll dp[N][2 * N];
ll inv [N];
ll add(ll a, ll b) {
return (a + b) % MOD;
}
ll binpow(ll base, int exp) {
ll ret = 1;
while(exp) {
if(exp & 1) {
ret = (ret * base) % MOD;
if(!ret) return ret;
}
exp >>= 1;
base = (base * base) % MOD;
}
return ret;
}
int main() {
scanf("%d", &n);
rep(i, 1, n + 1) {
scanf("%d%d", &q[i].X, &q[i].Y);
comp.pb(q[i].X); comp.pb(q[i].Y + 1);
}
sort(all(comp));
comp.erase(unique(all(comp)), comp.end());
rep(i, 2, n + 1) inv[i] = binpow(i, MOD - 2);
rep(i, 1, n + 1) {
q[i].X = lower_bound(all(comp), q[i].X) - comp.begin() + 1;
q[i].Y = lower_bound(all(comp), q[i].Y + 1) - comp.begin();
}
dist[0] = comp[0];
rep(i, 1, SZ(comp)) dist[i] = comp[i] - comp[i - 1];
//printf("compsz %d\n", SZ(comp));
rep(j, 0, SZ(comp)) dp[0][j] = 1;
rep(i, 1, n + 1) { // fiksiramo prefix
dp[i][0] = 1;
//printf("for %d is [%d,%d]\n", i, q[i].X, q[i].Y);
rep(j, q[i].X, q[i].Y + 1) { // fiksiramo kraj
dp[i][j] = add(dp[i][j], (dp[i - 1][j - 1] * dist[j]) % MOD); // ako samo sebe uzimamo
//printf("dp[%d][%d] -> %lld\n", i, j, dp[i][j]);
ll binom = dist[j] - 1; int cnt = 1;
per(k, i, 1) {
if(j >= q[k].X && j <= q[k].Y) {
binom = (binom * (dist[j] - 1 + cnt)) % MOD;
if(!binom) break;
binom = (binom * inv[++cnt]) % MOD;
dp[i][j] = add(dp[i][j], (dp[k - 1][j - 1] * binom) % MOD);
}
}
}
rep(j, 1, SZ(comp))
dp[i][j] = (dp[i][j] + dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1] + MOD) % MOD;
}
printf("%lld\n", ((ll)dp[n][SZ(comp) - 1] - 1 + MOD) % MOD);
return 0;
}
