#include <bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include "/home/eagle/ioi22/d2/debug.h"
#else
#define debug(...) void(37)
#endif
constexpr int md = int(1e9) + 7;
int add(int x, int y) {
if ((x += y) > md) {
x -= md;
}
return x;
}
int mul(int x, int y) {
return 1LL * x * y % md;
}
int power(int x, int p) {
int res = 1;
while (p > 0) {
if (p & 1) {
res = mul(res, x);
}
x = mul(x, x);
p >>= 1;
}
return res;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int N;
cin >> N;
vector<int> A(N), B(N);
for (int i = 0; i < N; ++i) {
cin >> A[i] >> B[i];
++B[i];
}
vector<int> inv(N + 1);
for (int i = 1; i <= N; ++i) {
inv[i] = power(i, md - 2);
}
debug(inv);
vector<int> ranges(2 * N);
for (int i = 0; i < N; ++i) {
ranges[2 * i] = A[i];
ranges[2 * i + 1] = B[i];
}
sort(ranges.begin(), ranges.end());
ranges.erase(unique(ranges.begin(), ranges.end()), ranges.end());
const int S = int(ranges.size());
vector<vector<int>> binom(S - 1, vector<int>(N + 1));
for (int i = 0; i < S - 1; ++i) {
int diff = ranges[i + 1] - ranges[i];
binom[i][0] = 1;
for (int j = 1; j <= min(N, diff); ++j) {
binom[i][j] = mul(mul(binom[i][j - 1], (diff - j + 1)), inv[j]);
}
}
vector<vector<int>> dp(S, vector<int>(N + 1));
for (int i = 0; i < S; ++i) {
dp[i][0] = 1;
}
for (int i = 0; i < N; ++i) {
int nw = 1;
for (int j = 0; j < S - 1; ++j) {
int a = 0;
bool in_range = (A[i] <= ranges[j] && ranges[j + 1] <= B[i]);
for (int k = N - 1; k > 0; --k) {
if (k != 0) {
a = add(a, mul(dp[j][k], binom[j][k]));
}
if (in_range) {
dp[j][k + 1] = add(dp[j][k + 1], dp[j][k]);
}
}
if (in_range) {
dp[j][1] = add(dp[j][1], nw);
}
nw = add(nw, a);
}
}
int ans = 0;
for (int i = 0; i < S - 1; ++i) {
for (int j = 1; j <= N; ++j) {
ans = add(ans, mul(dp[i][j], binom[i][j]));
}
}
cout << ans << '\n';
}
