#include <bits/stdc++.h>
#ifndef LOCAL
#include "gap.h"
#endif
using namespace std;
#define FOR(i, l, r) for(int i = (l); i < (r); ++i)
#define ROF(i, r, l) for(int i = (r)-1; i >= (l); --i)
#define mp make_pair
#define mt make_tuple
#define ff first
#define ss second
#define all(v) begin(v), end(v)
#define rall(v) rbegin(v), rend(v)
#define sz(v) (int)v.size()
#define pb push_back
#define eb emplace_back
#define compact(v) v.erase(unique(all(v)), end(v))
#define dbg(x) "[" #x " = " << (x) << "]"
template<typename T>
bool minimize(T& a, const T& b){
if(a > b) return a = b, true;
return false;
}
template<typename T>
bool maximize(T& a, const T& b){
if(a < b) return a = b, true;
return false;
}
typedef long long ll;
using db = double;
using ull = unsigned long long;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
using pd = pair<db, db>;
using vi = vector<int>;
using vl = vector<ll>;
using vc = vector<char>;
using vd = vector<db>;
using vb = vector<bool>;
using vpi = vector<pi>;
using vpl = vector<pl>;
void setIO(){
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef LOCAL
freopen("task.inp", "r", stdin);
freopen("task.out", "w", stdout);
#endif // LOCAL
}
const int mod = 1e9 + 7;
struct mint{
int v;
mint(int v = 0) : v(v) {}
mint& operator += (const mint& o){
v += o.v;
if(v >= mod) v -= mod;
return *this;
}
mint& operator -= (const mint& o){
v -= o.v;
if(v < 0) v += mod;
return *this;
}
mint& operator *= (const mint& o){
v = 1LL * v * o.v % mod;
return *this;
}
mint power(ll n) const{
mint res(1), base(*this);
for(; n > 0; n >>= 1, base *= base){
if(n & 1) res *= base;
}
return res;
}
mint inv() const {
return power(mod - 2);
}
mint& operator /= (const mint& o){
return *this *= o.inv();
}
friend mint operator + (mint a, const mint& b){ return a += b; }
friend mint operator - (mint a, const mint& b){ return a -= b; }
friend mint operator * (mint a, const mint& b){ return a *= b; }
friend mint operator / (mint a, const mint& b){ return a /= b; }
friend bool operator == (const mint& a, const mint& b){ return a.v == b.v; }
friend bool operator != (const mint& a, const mint& b){ return a.v != b.v; }
friend ostream& operator << (ostream& out, const mint& o){ return out << o.v; }
friend istream& operator >> (istream& in, mint& o){ return in >> o.v; }
};
const int MAX = 305;
int N, M, A[MAX], B[MAX], pos[MAX * 2][MAX], num[MAX * 2];
vi v;
mint fact[MAX], ifact[MAX], inv[MAX], dp[MAX][MAX * 2], sum_dp[MAX][MAX * 2];
mint f[MAX * 2][MAX], g[MAX * 2][MAX];
mint C(int n, int k){
if(n < k || k < 0) return 0;
if(n <= N) return fact[n] * ifact[n-k] * ifact[k];
assert(k <= N);
mint result = ifact[k];
FOR(i, 0, k) result *= mint(n - i);
return result;
}
void process_prefix_sum(int x){
sum_dp[x][0] = dp[x][0];
FOR(i, 1, M) sum_dp[x][i] = sum_dp[x][i-1] + dp[x][i];
}
int main(){
setIO();
cin >> N;
v.pb(0);
FOR(i, 1, N+1){
cin >> A[i] >> B[i];
++B[i];
//[A[i], B[i])
v.pb(A[i]);
v.pb(B[i]);
}
fact[0] = ifact[0] = 1;
FOR(i, 1, N+1) fact[i] *= fact[i-1];
ifact[N] = fact[N].inv();
ROF(i, N, 1) ifact[i] = ifact[i+1] * mint(i+1);
FOR(i, 1, N) inv[i] = ifact[i] * fact[i-1];
sort(all(v)); compact(v);
M = sz(v);
FOR(i, 1, M){
f[i][0] = 1;
FOR(j, 1, N+1){
f[i][j] = C(v[i+1] - v[i], j);
}
FOR(j, 2, N-1){
FOR(k, 0, j-1){
g[i][j] += C(j, k) * f[i][k+2];
}
}
}
dp[0][0] = 1;
process_prefix_sum(0);
FOR(i, 1, N+1){
A[i] = lower_bound(all(v), A[i]) - v.begin();
B[i] = lower_bound(all(v), B[i]) - v.begin();
FOR(j, 0, M){
dp[i][j] += dp[i-1][j];
if(A[i] <= j && j < B[i]){
pos[j][num[j]++] = i;
dp[i][j] += sum_dp[i-1][j-1] * mint(v[j+1] - v[j]); //only 1 in range [v[j], v[j+1])
FOR(pre, 0, num[j]-1){
int p = pos[j][pre], cur = num[j] - pre;
///dp[i][j] = sum_dp[pre-1][j-1] * \sum_{o = 0}^{cur-2} C(cur, o) * C(v[i+1] - v[i], o+2)
///fixed two endpoints
dp[i][j] += sum_dp[pre-1][j-1] * g[i][cur];
}
}
}
process_prefix_sum(i);
}
mint ans = sum_dp[N][M-1] - 1;
cout << ans << '\n';
return 0;
}
