#include <bits/stdc++.h>
#define a first
#define b second
using namespace std;
const long long INF = 1e18;
const int MOD = 1e9+7;
int n;
vector < map<int,int> > dp(1000);
vector < pair<int,int> > v(1000);
int main() {
cin >> n;
for(int i = 1; i <= n; i++)
cin >> v[i].a >> v[i].b;
map<int,int> :: iterator it;
for(int i = 1; i <= n; i++){
dp[i] = dp[i-1];
it = dp[i-1].begin();
int x = v[i].a;
while(it != dp[i-1].end()) {
if(it->first >= x) break;
dp[i][x] = (dp[i][x] + it->second) % MOD;
it++;
}
if(it != dp[i-1].end())
it++;
for(int j = v[i].a+1; j <= v[i].b; j++){
dp[i][j] = dp[i][j-1];
if(it != dp[i-1].end() && it->first < j){
dp[i][j] = (dp[i][j] + it->second) % MOD;
it++;
}
}
for(int j = v[i].a; j <= v[i].b; j++)
dp[i][j] = (dp[i][j]+1) % MOD;
}
it = dp[n].begin();
int ans = 0;
while(it != dp[n].end()) {
ans = (ans+(it->second)) % MOD;
//cout << it->second << " " << it->first << endl;
it++;
}
cout << ans;
}
