#include <bits/stdc++.h>
using namespace std;
#define int long long
#define valid(x, y) (a[x] <= pts[y] && pts[y+1] <= b[x]+1)
const int MOD = 1e9+7, LIM = 501;
int modInverse(int x){
int r = 1, p = (MOD - 2) * 2;
for(int y=x; p/=2; y=(y*y) % MOD)
if(p & 1) r = (r*y) % MOD;
return r;
}
int n, a[LIM], b[LIM], dp[LIM][LIM*2], F[LIM], invF[LIM], C[LIM*2][LIM];
vector<int> pts;
signed main(){
cin.tie(0)->sync_with_stdio(0);
cin >> n;
for(int i=0; i<n; ++i){
cin >> a[i] >> b[i];
pts.push_back(a[i]);
pts.push_back(b[i]+1);
}
sort(pts.begin(), pts.end());
pts.resize(unique(pts.begin(), pts.end()) - pts.begin());
int m = size(pts) - 1, ans = 0;
F[0] = invF[0] = 1;
for(int i=1; i<=n; ++i){
F[i] = (F[i-1] * i) % MOD;
invF[i] = modInverse(F[i]);
}
for(int i=0; i<m; ++i){
int diff = pts[i+1] - pts[i];
int p = 1;
for(int j=1; j<=n; ++j){
(p *= diff - j + 1) %= MOD;
C[i][j] = (p * invF[j]) % MOD;
}
}
for(int i=0; i<n; ++i){
for(int k=0; k<m; ++k){
if(!valid(i, k)) continue;
int cnt = 1, p = C[k][1];
for(int j=i; --j>=0; ){
if(k) (dp[i][k] += dp[j][k-1] * cnt) %= MOD;
if(valid(j, k)) p += C[k][++cnt];
}
(dp[i][k] += p) %= MOD;
(ans += dp[i][k]) %= MOD;
}
for(int k=1; k<m; ++k) (dp[i][k] += dp[i][k-1]) %= MOD;
}
cout << (ans % MOD + MOD) % MOD;
}
