#include <bits/stdc++.h>
#define ar array
//#define int long long
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const ll inf = 1e18;
const int N = 1e5 + 5;
ll add(ll a, ll b) {
return a + b - (a + b >= mod ? mod : 0);
}
ll mul(ll a, ll b) {
return a * b % mod;
}
ll exp(ll a, ll b) {
ll ans = 1;
while(b) {
if(b & 1) ans = ans * a % mod;
a = a * a % mod;
b /= 2;
}
return ans;
}
ll fac[N], inv[N];
ll C(int n, int k) {
if(n < k) return 0;
return fac[n] * inv[k] % mod * inv[n-k];
}
ll dp[505][1005];
vector<int> cmp;
int n, L[N], R[N], m;
signed main() {
fac[0] = inv[0] = 1;
for(int i=1; i<N; i++) {
fac[i] = fac[i-1] * i % mod;
inv[i] = exp(fac[i], mod - 2);
}
cin >> n;
set<int> st = { 0 };
for(int i=1; i<=n; i++) {
cin >> L[i] >> R[i];
st.insert(L[i]);
st.insert(++R[i]);
}
cmp = vector<int>( st.begin(), st.end() );
for(int i=1; i<=n; i++) {
L[i] = lower_bound(cmp.begin(), cmp.end(), L[i]) - cmp.begin();
R[i] = lower_bound(cmp.begin(), cmp.end(), R[i]) - cmp.begin() - 1;
}
m = cmp.size() - 1;
memset(dp, 0, sizeof(dp));
dp[0][0] = 1;
for(int i=1; i<=n; i++) {
for(int j=1; j<=m; j++)
dp[i-1][j] = add(dp[i-1][j-1], dp[i-1][j]);
for(int j=L[i]; j<=R[i]; j++) {
int cnt = 0;
for(int k=i; k>=1; k--) {
if(L[k] <= j && j <= R[k]) cnt++;
dp[i][j] = add(dp[i][j], mul(dp[k-1][j-1], C(cmp[j+1]-cmp[j]+cnt-1, cnt)));
}
}
}
ll ans = 0;
for(int j=1; j<=m; j++)
dp[n][j] = add(dp[n][j], dp[n][j-1]);
for(int i=1; i<=n; i++)
ans = add(ans, dp[i][m]);
cout << ans << '\n';
}
