#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef pair<int,int> pi;
typedef vector<pi> pii;
typedef tuple<ll,ll,ll> ti;
typedef vector<ll> li;
typedef vector<li> lii;
#define REP(i,a,b) for(int i=a;i<b;i++)
#define F first
#define S second
#define PB push_back
#define LSOne(s) ((s)&(-s))
ll INF=1000000000000000010;
int inf=1e9+10;
ll M=1e9+7;
int main() {
// ios::sync_with_stdio(0);
// cin.tie(0);
int n;cin>>n;
vector<pi> a(n);
REP(i,0,n)cin>>a[i].F>>a[i].S;
vector<vector<pair<int,ll>>> dp(n);
REP(i,0,n){
int c=0;
REP(k,a[i].F,a[i].S+1){
dp[i].PB({k,1});
REP(j,0,i){
auto it=upper_bound(dp[j].begin(),dp[j].end(),make_pair(k,-1LL));
ll val=0;
if(it!=dp[j].begin()){
it--;
val=it->second;
}
dp[i][c].S+=val;
dp[i][c].S%=M;
}
if(c!=0){
dp[i][c].S+=dp[i][c-1].S;
dp[i][c].S%=M;
}
c++;
}
}
ll ans=0;
REP(i,0,n){
ans+=dp[i].back().S;
ans%=M;
}
cout<<ans;
}
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