#include <bits/stdc++.h>
using namespace std;;
#define ll long long
#define ar array
#define ld double
#define int long long
#define all(v) v.begin(), v.end()
// #pragma GCC optimize("O3,Ofast,unroll-loops ")
const int N = 3010;
const int M = 20;
const int LOG = 20;
const int INF = 1e17;
int MOD = 1e9 + 7;
const ld EPS = 1e-12;
template<typename T>
inline void chmin(T &x,T y){x = min(x, y);}
template<typename T>
inline void chmax(T &x,T y){x = max(x, y);}
inline void mm(int &x){x = (x % MOD + MOD) % MOD;};
int W(int l1,int r1,int l2,int r2){
int a = max(l1, l2 + 1);
int b = min(r1, r2);
int c = max(r2 + 1, l1);
int x = r2 - l2 + 1;
int u = max(0ll, b - a + 1) * (a + b - 2 * l2) / 2;
int v = max(0ll, r1 - c + 1) * x;
mm(u);
mm(v);
return (u + v) % MOD;
}
int inv[N];
int P(int a,int b){
int ans = 1;
while(b){
if(b % 2)mm(ans *= a);
b /= 2;
mm(a *= a);
}
return ans;
}
void orz(){
inv[0] = 1;
for(int i = 1;i < N;i++)inv[i] = P(i, MOD - 2);
int n;
cin>>n;
int L[n + 1], R[n + 1];
// cout<<P(2, 5)<<'\n';
for(int i = 1;i <= n;i++)cin>>L[i]>>R[i];
vector<int> v;
for(int i = 1;i <= n;i++)v.push_back(L[i]), v.push_back(R[i] + 1);
sort(all(v));
v.erase(unique(all(v)), v.end());
vector<ar<int,2>> S = {{0, 0}};
for(int i = 0;i + 1 < v.size();i++)S.push_back({v[i], v[i + 1] - 1});
int m = S.size();
int dp[n + 1][m];
memset(dp, 0, sizeof dp);
for(int i = 0;i < m;i++)dp[0][i] = 1;
for(int i = 1;i <= n;i++){
dp[i][0] = 1;
for(int j = 1;j < m;j++){
dp[i][j] = dp[i][j - 1];
auto [l, r] = S[j];
int cnt = 0, mult = 1;
for(int k = i;k;k--){
if(L[k] <= l && r <= R[k]){
cnt++;
mm(mult *= ((r - l + cnt) * inv[cnt]) % MOD);
mm(dp[i][j] += (dp[k - 1][j - 1] * mult) % MOD);
}
}
}
}
int ans = dp[n][m - 1];
mm(ans -= 1);
cout<<ans;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int t = 1;
// cin>>t;
while (t--)orz();
}
