#include <iostream>
#include <map>
using namespace std;
#define int long long
const int N = 505;
int l[N], r[N], Sz[N<<2], cur, dp[N][N<<2], ways[N<<2][N], inv[N], mod = 1e9 + 7;
map<int, int> mp, mp2;
int power(int a, int b){
if (b == 1)
return a;
int ans = power(a, b / 2);
ans = ans * ans % mod;
if (b % 2)
ans = ans * a % mod;
return ans;
}
signed main(){
for (int i=1;i<N;i++)
inv[i] = power(i, mod - 2);
int n, lst = -1, Ans = 0;
cin>>n;
for (int i=1;i<=n;i++){
cin>>l[i]>>r[i];
mp[l[i] - 1];
mp[r[i]];
}
for (auto [i, j] : mp){
mp2[i] = ++cur;
if (lst == -1)
Sz[cur] = 1;
else
Sz[cur] = i - lst;
lst = i;
}
for (int i=1;i<=n;i++){
l[i] = mp2[l[i] - 1] + 1;
r[i] = mp2[r[i]];
}
for (int i=1;i<=cur;i++){
for (int m=0;m<=n;m++){
int ch1 = 1, ch2 = 1;
for (int j=0;j<=min(m, Sz[cur] - 1);j++){
ch1 = ch1 * (Sz[i] - j) % mod * inv[j + 1] % mod;
ways[i][m] = (ways[i][m] + ch1 * ch2) % mod;
ch2 = ch2 * (m - j) % mod * inv[j + 1] % mod;
}
}
}
for (int j=0;j<=cur;j++)
dp[0][j] = 1;
for (int i=1;i<=n;i++){
for (int cr=l[i];cr <= r[i];cr++){
int m = 0;
for (int j=i-1;j>=0;j--){
dp[i][cr] = (dp[i][cr] + dp[j][cr - 1] * ways[cr][m]) % mod;
m += (cr >= l[j] and cr <= r[j]);
}
Ans += dp[i][cr];
}
for (int j=1;j<=cur;j++)
dp[i][j] = (dp[i][j-1] + dp[i][j]) % mod;
}
cout<<Ans<<'\n';
}
