#include <bits/stdc++.h>
using namespace std;
#define int long long
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];
bool valid[LIM];
vector<int> pts;
int nCr(int x, int y){
return (((F[x] * invF[y]) % MOD) * invF[x-y]) % MOD;
}
void add(int &x, int y){
x += y;
while(x >= MOD) x -= MOD;
while(x <=-MOD) x += MOD;
}
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 k=0; k<m; ++k){
for(int i=1; i<=n; ++i){
int p = 1; C[i] = 0;
for(int j=1; j<=i; ++j){
(p *= pts[k+1] - pts[k] - j + 1) %= MOD;
(C[i] += ((p * invF[j]) % MOD) * nCr(i-1, j-1)) %= MOD;
}
}
for(int i=0; i<n; ++i){
valid[i] = a[i] <= pts[k] && pts[k+1] <= b[i]+1;
}
for(int i=0; i<n; ++i){
if(valid[i]){
int cnt = 1;
for(int j=i; --j>=0; ){
if(k) add(dp[i][k], dp[j][k-1] * C[cnt]);
cnt += valid[j];
}
add(dp[i][k], C[cnt]);
add(ans, dp[i][k]);
}
if(k){
add(dp[i][k], dp[i][k-1]);
}
}
}
cout << (ans % MOD + MOD) % MOD;
}
