#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define sp << " " <<
#define all(x) x.begin(),x.end()
#define big(x) ((int)(x.size()))
using namespace std;
const int MOD = 1e9+7, LIM = 2e6+1, inf = 2e9;
int add(int x,int y) {
if ((x + y) >= MOD) return x + y - MOD;
return x + y;
}
int mult(int x,int y) {
return (1LL * x * y) % MOD;
}
int expo(int x,int y) {
if (!y) return 1;
int e = expo(x, y >> 1);
e = mult(e, e);
if (y & 1) e = mult(e, x);
return e;
}
int divide(int x, int y) {
return mult(x, expo(y, MOD - 2));
}
void solve() {
int n;
cin >> n;
vi a(n+1),b(n+1);
vi v;
for (int i=1;i<=n;i++) cin >> a[i] >> b[i];
for (int i=1;i<=n;i++) v.push_back(a[i]-1);
for (int i=1;i<=n;i++) v.push_back(b[i]);
sort(all(v));
v.erase(unique(all(v)),v.end());
int sz = big(v);
int cho[sz+1][n+1]{};
for (int i=2;i<=sz;i++) {
cho[i][1] = v[i-1]-v[i-2];
for (int j=2;j<=n;j++) {
cho[i][j] = cho[i][j-1];
cho[i][j] = mult(cho[i][j],v[i-1]-v[i-2]+j-1);
cho[i][j] = mult(cho[i][j],divide(1,j));
}
}
int dp[n+1][sz+1]{};
for (int i=0;i<=sz;i++) dp[0][i] = 1;
for (int i=1;i<=n;i++) {
dp[i][0] = 1;
for (int j=1;j<=sz;j++) {
dp[i][j] = dp[i][j-1];
int nm = 0;
for (int k = i;k>=1;k--) {
if (a[k] <= v[j-1] && b[k] >= v[j-1]) {
nm++;
dp[i][j] = add(dp[i][j],mult(cho[j][nm],dp[k-1][j-1]));
}
}
}
}
cout << add(dp[n][sz],MOD-1) << '\n';
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef Dodi
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
