#include <bits/stdc++.h>
using namespace std;
#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for (int i=(a);i>=(b);--i)
const int MX_N = 505;
const int MOD = 1e9+7;
int N, A[MX_N], B[MX_N];
vector<int> val;
int dp[MX_N][2*MX_N];
int pre[MX_N][2*MX_N];
int inv[MX_N];
map<int,vector<int>> nck;
map<int,vector<int>> prod;
void precomp(int n) {
if (nck.count(n)) return;
auto& v = nck[n];
v.assign(N+1,1);
FOR(k,1,N) v[k] = 1LL * v[k-1] * (n-k+1) % MOD * inv[k] % MOD;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> N;
FOR(i,1,N){
cin >> A[i] >> B[i];
B[i] += 1;
val.push_back(A[i]);
val.push_back(B[i]);
}
sort(ALL(val));
val.resize(unique(ALL(val))-val.begin());
FOR(i,1,N){
A[i] = lower_bound(ALL(val),A[i])-val.begin();
B[i] = lower_bound(ALL(val),B[i])-val.begin();
}
inv[1] = 1;
FOR(i,2,N) inv[i] = (MOD - 1LL * (MOD/i) * inv[MOD%i] % MOD) % MOD;
FOR(i,0,N) precomp(i);
FOR(i,1,SZ(val)-1) precomp(val[i]-val[i-1]);
FOR(i,1,SZ(val)-1){
precomp(val[i]-val[i-1]);
auto& u = nck[val[i]-val[i-1]];
auto& v = prod[val[i]-val[i-1]];
v.assign(N+1,0);
FOR(x,0,N-2){
auto& w = nck[x];
FOR(k,0,x){
v[x] += 1LL * u[k+2] * w[k] % MOD;
v[x] %= MOD;
}
}
}
RFOR(x,SZ(val)-1,0){
dp[N+1][x] = 1;
pre[N+1][x] = dp[N+1][x];
}
RFOR(i,N,1){
RFOR(x,SZ(val)-1,0){
dp[i][x] = 0;
if (x+1 < SZ(val)) dp[i][x] = (dp[i][x] + dp[i][x+1]) % MOD;
if (A[i] <= x && x < B[i]) {
FOR(j,i,N){
if (A[i] > x || B[i] <= x) break;
int coeff = 0;
if (i == j) {
coeff = val[x+1]-val[x];
} else {
coeff = prod[val[x+1]-val[x]][j-i-1];
}
int sum = (pre[j+1][x+1] - pre[N+2][x+1] + MOD) % MOD;
dp[i][x] = (dp[i][x] + 1LL * coeff * sum % MOD) % MOD;
}
}
pre[i][x] = (pre[i+1][x] + dp[i][x]) % MOD;
//TRACE(i _ x _ dp[i][x]);
}
}
int ans = 0;
FOR(i,1,N){
ans = (ans + dp[i][0]) % MOD;
}
cout << ans;
}
