#include <iostream>
#include <algorithm>
using namespace std;
constexpr int N = 500;
constexpr int P = 1e9 + 7;
int n;
pair<int, int> intervals[N];
int poi[N * 2];
int inverse[N + 1];
inline int divide(int y, int x) {
for (int k = P - 2; k; k >>= 1) {
if (k & 1)
y = (long long) y * x % P;
x = (long long) x * x % P;
}
return y;
}
struct {
int d;
int b[N + 1];
int c[N + 2];
void init(int R) {
b[0] = 1;
for (int k = 1; k <= n; k++) {
b[k] = (long long) (R + k) * b[k - 1] % P * inverse[k] % P;
}
d = n + 1;
}
operator int() {
return c[1] - c[0];
}
void operator+=(int x) {
for (int k = 0; k < d; k++) {
c[k] = (c[k + 1] + (long long) x * b[k]) % P;
}
d--;
}
} dp[2 * N];
signed main()
{
ios::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
// freopen("input.txt", "r", stdin);
cin >> n;
for (int x = 1; x <= n; x++) {
inverse[x] = divide(1, x);
}
for (int i = 0; i < n; i++) {
auto &[l, r] = intervals[i];
cin >> l >> r;
r++;
poi[i * 2] = l;
poi[i * 2 + 1] = r;
}
sort(poi, poi + 2 * n);
int m = unique(poi, poi + 2 * n) - poi - 1;
for (int j = 0; j < m; j++) {
dp[j].init(poi[j + 1] - poi[j]);
}
for (int i = 0; i < n; i++) {
auto [l, r] = intervals[i];
long long s = 1;
int j = 0;
for (; poi[j] < l; j++) {
s += dp[j];
}
s %= P;
for (; poi[j] < r; j++) {
int t = (s + dp[j]) % P;
dp[j] += s;
s = t;
}
}
long long res = 0;
for (int j = 0; j < m; j++) {
res += dp[j];
}
cout << (res % P + P) % P;
return 0;
}
