#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
#include <random>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
const int MOD = 1000000007;
int inv(int num){
int p=MOD, res=1, y=0;
while (num>1){
int q=num/p, t=p;
p=num%p, num=t, t=y, y=res-q*y, res=t;
}
if (res<0)res+=MOD;
return res;
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
vector<int> ord;
vector<pii> vect(n+1);
for (int i=1; i<=n; ++i)cin>>vect[i].fi>>vect[i].se, --vect[i].fi, ord.pb(vect[i].fi), ord.pb(vect[i].se);
sort(ord.begin(), ord.end());
ord.erase(unique(ord.begin(), ord.end()), ord.end());
vector<vector<int> > ncr(ord.size(), vector<int>(n+1)), dp(n+1, vector<int>(ord.size(), 0));
for (int i=1; i<ord.size(); ++i){
ncr[i][1]=(ord[i]-ord[i-1])%MOD;
for (int j=2; j<=n; ++j)ncr[i][j]=(((((ncr[i][j-1]*(ord[i]-ord[i-1]-j+1))%MOD)*inv(j))%MOD)+MOD)%MOD;
}
for (int i=0; i<ord.size(); ++i)dp[0][i]=1;
for (int i=1; i<=n; ++i)dp[i][0]=1;
for (int i=1; i<=n; ++i)for (int j=1; j<ord.size(); ++j){
dp[i][j]=dp[i][j-1];
for (int p=i, sz=0; p>=1; --p)if (vect[p].fi<ord[j]&&ord[j]<=vect[p].se)++sz, dp[i][j]=(dp[i][j]+dp[p-1][j-1]*ncr[j][sz])%MOD;
}
cout<<dp[n][ord.size()-1];
}
