#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cmath>
#include <iomanip>
#include <cassert>
#include <bitset>
using namespace std;
typedef pair<int, int> P;
#define rep(i, n) for (int i=0; i<(n); i++)
#define all(c) (c).begin(), (c).end()
#define uniq(c) c.erase(unique(all(c)), (c).end())
#define index(xs, x) (int)(lower_bound(all(xs), x) - xs.begin())
#define _1 first
#define _2 second
#define pb push_back
#define INF 1145141919
#define MOD 1000000007
inline void add(int &x, int v) { x += v; if (x >= MOD) x -= MOD; }
struct BIT {
int n;
vector<int> xs;
BIT(int n) : n(n) {
xs.resize(n+1);
}
void addV(int i, int v) {
for (int x=i+1; x<=n; x+=x&-x) add(xs[x], v);
}
int sum(int i) {
int s = 0;
for (int x=i+1; x>0; x-=x&-x) add(s, xs[x]);
return s;
}
};
int N;
int A[500], B[500];
signed main() {
ios::sync_with_stdio(false); cin.tie(0);
cin >> N;
vector<int> xs;
xs.pb(0);
rep(i, N) {
cin >> A[i] >> B[i];
for (int x=A[i]; x<=B[i]; x++) xs.pb(x);
}
sort(all(xs)); uniq(xs);
BIT bit(xs.size());
bit.addV(0, 1);
rep(i, N) {
int p = lower_bound(all(xs), B[i]) - xs.begin();
for (int x=B[i]; x>=A[i]; x--) {
bit.addV(p, bit.sum(p-1));
p--;
}
}
int s = bit.sum(xs.size()-1);
add(s, MOD-1);
cout << s << "\n";
return 0;
}
