/**
* IT'S YA BOI KOSEH!!
* 2026-03-31-22.17
**/
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define ppb pop_back
#define pf push_front
#define ppf pop_front
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define upb upper_bound
#define lwb lower_bound
#define FILE(task) freopen(task".inp","r",stdin);freopen(task".out","w",stdout);
#define int ll
typedef long long ll;
typedef long double lldb;
///--------------------------------------------------------------------------------///
//VARIABLES
const int MOD = 1e9 + 7;
const int MAXN = 505;
int n;
pair<int, int> a[MAXN];
vector<int> b;
pair<int, int> range[MAXN];
int dp[MAXN][2005];
int inv[MAXN];
int vLen[MAXN];
//FUNCTIONS
int binPow(int x, int y)
{
int res = 1;
while (y)
{
if (y & 1) res = (1LL * res * x) % MOD;
x = (1LL * x * x) % MOD;
y >>= 1;
}
return res;
}
int C(int n, int k)
{
if (k > n) return 0;
k = min(k, n - k);
long long res = 1;
for (int i = 1; i <= k; i++)
{
res = res * ((n - k + i) % MOD) % MOD;
res = res * inv[i] % MOD;
}
return (int)res;
}
//PROCESS
void read()
{
cin >> n;
for (int i = 1; i <= n; i++)
{
cin >> a[i].first >> a[i].second;
b.pb(a[i].first);
b.pb(a[i].second + 1);
}
}
void solve()
{
for (int i = 1; i <= n; i++) inv[i] = binPow(i, MOD - 2);
sort(all(b));
b.erase(unique(all(b)), b.end());
int m = b.size();
for (int i = 1; i <= n; i++)
{
range[i].first = lower_bound(all(b), a[i].first) - b.begin();
range[i].second = lower_bound(all(b), a[i].second + 1) - b.begin() - 1;
}
vLen[0] = 1;
for (int i = 0; i < m - 1; i++)
{
int len = b[i + 1] - b[i];
for (int j = 1; j <= n; j++)
{
int cnt = 0;
if (a[j].first <= b[i] && b[i + 1] - 1 <= a[j].second)
{
cnt = 1;
int cur = len;
for (int k = j - 1; k >= 0; k--)
{
dp[j][i] = (dp[j][i] + vLen[k] * cur % MOD) % MOD;
if(a[k].first <= b[i] and b[i + 1] - 1 <= a[k].second)
{
cnt++;
cur = (len + cnt - 1) * cur % MOD * inv[cnt] % MOD;
}
}
}
}
for (int j = 1; j <= n; j++) vLen[j] = (vLen[j] + dp[j][i]) % MOD;
}
int ans = 0;
for (int i = 1; i <= n; i++) ans = (ans + vLen[i]) % MOD;
cout << ans;
}
//MAIN
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
//FILE("test");
bool t_case = false;
int tCase = 1;
if (t_case) cin >> tCase;
while (tCase--)
{
read();
solve();
}
return 0;
}
