#include <bits/stdc++.h>
using namespace std;
const int M = 1e9 + 7;
int add(int a, int b) {
return a + b < M ? a + b : a + b - M;
}
int sub(int a, int b) {
return a - b >= 0 ? a - b : a - b + M;
}
int mul(int a, int b) {
return a * 1ll * b % M;
}
int pw(int a, int n) {
int res = 1;
for (; n > 0; n >>= 1, a = mul(a, a)) {
if (n & 1) {
res = mul(res, a);
}
}
return res;
}
int inv(int a) {
return pw(a, M - 2);
}
const int N = 505;
int n;
int a[N], b[N];
int m;
int x[2 * N];
int len[2 * N];
int bigc[2 * N][N];
int c[N][N];
int sumc[2 * N][N];
int dp[2 * N][N];
int pref[N];
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n;
for (int i = 0; i < n; ++i) {
cin >> a[i] >> b[i];
++b[i];
}
for (int i = 0; i < n; ++i) {
x[2 * i] = a[i];
x[2 * i + 1] = b[i];
}
sort(x, x + 2 * n);
m = unique(x, x + 2 * n) - x - 1;
for (int i = 0; i < m; ++i) {
len[i] = x[i + 1] - x[i];
bigc[i][0] = 1;
for (int j = 1; j <= min(len[i], n); ++j) {
bigc[i][j] = mul(bigc[i][j - 1], mul(len[i] - j + 1, inv(j)));
}
}
c[0][0] = 1;
for (int i = 1; i <= n; ++i) {
c[i][0] = c[i][i] = 1;
for (int j = 1; j < i; ++j) {
c[i][j] = add(c[i - 1][j - 1], c[i - 1][j]);
}
}
for (int i = 0; i < m; ++i) {
for (int j = 1; j <= n; ++j) {
for (int k = 1; k <= min(len[i], j); ++k) {
sumc[i][j] = add(sumc[i][j], mul(bigc[i][k], c[j - 1][k - 1]));
}
}
}
for (int j = 0; j < m; ++j) {
for (int i = 0; i < n; ++i) {
pref[i + 1] = pref[i] + (x[j] >= a[i] && x[j + 1] <= b[i]);
}
for (int i = 0; i < n; ++i) {
if (x[j] >= a[i] && x[j + 1] <= b[i]) {
dp[j][i] = sumc[j][pref[i + 1]];
}
}
if (j > 0) {
for (int i = 0; i < n; ++i) {
if (x[j] >= a[i] && x[j + 1] <= b[i]) {
for (int k = 0; k < i; ++k) {
dp[j][i] = add(dp[j][i], mul(dp[j - 1][k], sumc[j][pref[i + 1] - pref[k + 1]]));
}
}
}
for (int i = 0; i < n; ++i) {
dp[j][i] = add(dp[j][i], dp[j - 1][i]);
}
}
}
int ans = 0;
for (int i = 0; i < n; ++i) {
ans = add(ans, dp[m - 1][i]);
}
cout << ans << endl;
return 0;
}
