#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define int ll
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vi> vvi;
typedef vector<vii> vvii;
#define INF INT_MAX
#define MOD 1000000007
#define all(x) x.begin(), x.end()
int MULT(){return 1;}
template<typename T, typename... Args>
int MULT(T v, Args... args){
return (v*MULT(args...))%MOD;
}
int binexp(int base, int pow, int M=MOD){
int res = 1;
while(pow){
if(pow & 1) res *= base;
pow >>= 1, base *= base;
if(M) base %= M, res %= M;
}
return res;
}
constexpr int fac(int n){
if(n == 0) return 1;
return MULT(n, fac(n-1));
}
int nCk(int n, int k){
return MULT(fac(n), binexp(fac(k), MOD-2), binexp(fac(n-k), MOD-2));
}
vii A; vi B; vvi dp;
int solve(int n, int c){
if(n == -1) return 1;
if(c == 0) return 1;
if(dp[n][c] != -1)
return dp[n][c];
auto &v = dp[n][c]; v = solve(n, c-1);
for(int x = n, cnt = 0; x >= 0; x--){
if(!(A[x].first <= B[c-1] and B[c] <= A[x].second))
continue;
for(int k = 0; k <= min(cnt, B[c]-B[c-1]-1); k++)
v += MULT(nCk(B[c]-B[c-1], k+1), nCk(cnt, k), solve(x-1, c-1)), v %= MOD;
cnt++;
}
return v;
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
int N; cin >> N;
A.resize(N);
for(auto &[l, r] : A){
cin >> l >> r; r++;
B.push_back(l); B.push_back(r);
}
sort(all(B));
dp.resize(N, vi(B.size(), -1));
cout << solve(N-1, B.size()-1)-1 << endl;
return 0;
}
