#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll, ll>
#define fi first
#define sec second
#define ld long double
const int MAXN = 5e2;
const ll INF = 4e18;
const int MOD = 1e9 + 7;
int dp[MAXN + 5][1005], ps[MAXN + 5][1005];
ll comb[1005][MAXN + 5], inv[MAXN + 5], fc[MAXN + 5];
int A[MAXN + 5], B[MAXN + 5];
int prec[1005][MAXN + 5][2];
ll expo(ll a, ll b){
ll ans = 1;
for(;b > 0;){
if(b & 1) ans = ans * a % MOD;
a = a * a % MOD;
b /= 2;
}
return ans;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int tc = 1;
// cin >> tc;
fc[0] = 1;
for(int i = 1; i <= MAXN; i++){
fc[i] = fc[i - 1] * i % MOD;
}
inv[MAXN] = expo(fc[MAXN], MOD - 2);
for(int i = MAXN - 1; i >= 0; --i){
inv[i] = inv[i + 1] * (i + 1) % MOD;
}
for(;tc--;){
int N; cin >> N;
vector<int> comp;
comp.push_back(0);
for(int i = 1; i <= N; i++){
cin >> A[i] >> B[i];
comp.push_back(A[i]), comp.push_back(B[i] + 1);
}
sort(comp.begin(), comp.end());
comp.erase(unique(comp.begin(), comp.end()), comp.end());
auto get = [&](int idx){
return lower_bound(comp.begin(), comp.end(), idx) - comp.begin() + 1;
};
dp[0][get(0)] = ps[0][get(0)] = 1;
int M = comp.size();
for(int i = 1; i <= M; i++) ps[0][i] += ps[0][i - 1];
auto C = [&](int n, int r){
if(n < 0 || r < 0 || n < r) return 0LL;
return fc[n] * inv[r] % MOD * inv[n - r] % MOD;
};
comb[M][0] = comb[M][1] = 1;
for(int i = 1; i <= M; i++){
for(int j = 1; j <= min(N, comp[i] - comp[i - 1]); j++){
if(i < M){
comb[M][0] = 1;
int res = comp[i] - comp[i - 1], num = min(j, res - j);
comb[i][j] = inv[num];
for(int k = res; k > res - num; --k){
comb[i][j] = comb[i][j] * k % MOD;
}
}
for(int k = 0; k <= j; k++){
// 0 -> kalau start == end
prec[i][j][0] = (prec[i][j][0] + C(j - 1, k - 1) * comb[i][k] % MOD);
if(prec[i][j][0] >= MOD) prec[i][j][0] -= MOD;
// 1 -> kalau start != end
prec[i][j][1] = (prec[i][j][1] + C(j - 2, k - 2) * comb[i][k] % MOD);
if(prec[i][j][1] >= MOD) prec[i][j][1] -= MOD;
}
}
}
for(int i = 1; i <= N; i++){
A[i] = get(A[i]);
B[i] = get(B[i] + 1) - 1;
for(int j = 1; j <= M; j++){
dp[i][j] = dp[i - 1][j];
if(A[i] <= j && j <= B[i]){
int cnt = 0;
for(int k = i; k >= 1; --k){
if(A[k] <= j && j <= B[k]){
cnt++;
if(k == i){
dp[i][j] += 1LL * ps[k - 1][j - 1] * prec[j][cnt][0] % MOD;
if(dp[i][j] >= MOD) dp[i][j] -= MOD;
}
else{
dp[i][j] += 1LL * ps[k - 1][j - 1] * prec[j][cnt][1] % MOD;
if(dp[i][j] >= MOD) dp[i][j] -= MOD;
}
}
}
}
ps[i][j] = (ps[i][j - 1] + dp[i][j]);
if(ps[i][j] >= MOD) ps[i][j] -= MOD;
}
}
// cout << dp[1][2] << "\n";
cout << (ps[N][M] - 1LL + MOD) % MOD << "\n";
}
}
/*
5 + 5 + 10 = 20?
*/
