#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define int long long
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<pii> vii;
typedef vector<bool> vb;
typedef tree<pii,null_type,less<pii>,rb_tree_tag,
tree_order_statistics_node_update> oset;
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define mid (l+r)/2
#define all(x) x.begin(),x.end()
#define FOR(i,a) for(int i=0;i<(a);i++)
#define FORE(i,a,b) for(int i=(a);i<(b);i++)
#define cont(x) for(auto el:x) cout<<el<<' ';cout<<endl;
#define contp(x) for(auto el:x) cout<<el.fi<<'-'<<el.se<<' ';cout<<endl;
#define sp <<" "<<
#define DEBUG(x) cout<<(#x) sp x<<endl
#define carp(a,b) (((a%MOD)*(b%MOD))%MOD)
#define topla(a,b) (((a%MOD)+(b%MOD))%MOD)
const int INF=1e18;
const int MAXN=505;
const int MOD=1e9+7;
int dp[MAXN][MAXN];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
vi a(n+1),b(n+1);
FORE(i,1,n+1) cin>>a[i]>>b[i];
FOR(i,n+1){
dp[i][0]=0;
FORE(j,1,n+1){
dp[i][j]=INF;
}
}
int ans=0;
FORE(i,1,n+1){
FORE(j,1,i){
FORE(tane,1,j+1){
if(dp[j][tane]==INF) continue;
if(dp[j][tane]>b[i]) continue;
ans++;
ans%=MOD;
if(dp[j][tane]<=a[i]){
dp[i][tane+1]=min(dp[i][tane+1],a[i]);
}
else{
dp[i][tane+1]=min(dp[i][tane+1],dp[j][tane]);
}
}
}
if(dp[i][1]==INF){
ans++;
ans%=MOD;
}
dp[i][1]=min(dp[i][1],a[i]);
}
cout<<ans<<endl;
}
