#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

typedef long long LL;

const int N = 505, P = 1e9 + 7, INF = 2e9;

int n, a[N], b[N], d[N << 1], f[N], tot, g[N];

int inline power(int a, int b) {
	int res = 1;
	while (b) {
		if (b & 1) res = (LL)res * a % P;
		a = (LL)a * a % P;
		b >>= 1;
	}
	return res;
}

int main() {
	scanf("%d", &n);
	for (int i = 1; i <= n; i++)
		scanf("%d%d", a + i, b + i), d[++tot] = a[i], d[++tot] = b[i] + 1;
	sort(d + 1, d + 1 + tot);
	tot = unique(d + 1, d + 1 + tot) - d - 1;
	f[0] = 1;
	for (int j = 1; j < tot; j++) {
		int L = d[j + 1] - d[j];
		g[0] = 1;
		for (int i = 1; i <= n; i++)
			g[i] = (LL)g[i - 1] * (L + i - 1) % P * power(i, P - 2) % P;
		for (int i = n; i; i--) {
			if (a[i] > d[j] || d[j + 1] - 1 > b[i]) continue;
			int cnt = 0;
			for (int k = i - 1; ~k; k--) {
				if (a[k + 1] <= d[j] && d[j + 1] - 1 <= b[k + 1]) cnt++;
				f[i] = (f[i] + (LL)f[k] * g[cnt]) % P;
			}
		}
	}
	int ans = 0;
	for (int i = 1; i <= n; i++) (ans += f[i]) %= P;
	printf("%d\n", ans);
	return 0;
}