#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
long long N, A[509], B[509], nr1[1009][1009], nr2[1009][1009], dp[1009][1009], inv[1009], mod = 1000000007; vector<long long>V;
long long rets[1009][1009];
long long modpow(long long a, long long b, long long m) {
long long p = 1, q = a;
for (int i = 0; i < 60; i++) {
if ((b / (1LL << i)) % 2 == 1) { p *= q; p %= m; }
q *= q; q %= m;
}
return p;
}
long long Div(long long a, long long b, long long m) {
return (a*modpow(b, m - 2, m)) % m;
}
void init() {
for (int i = 0; i <= 500; i++) {
for (int j = 0; j <= 500; j++) {
if (i == 0 || j == 0) nr1[i][j] = 1;
else nr1[i][j] = (nr1[i - 1][j] + nr1[i][j - 1]) % mod;
}
}
for (int i = 1; i <= 1000; i++) inv[i] = Div(1, i, mod);
for (int i = 0; i < V.size() - 1; i++) {
long long L = V[i + 1] - V[i], S = 1;
for (int j = 0; j <= 500; j++) {
if (L < j) break;
nr2[i][j] = S;
S *= (L - j); S %= mod;
S *= inv[j + 1]; S %= mod;
}
}
}
long long ncr(long long n, long long r) {
if (r < 0 || n < r) return 0;
return nr1[n - r][r];
}
long long solve(long long v, long long pos) {
if (rets[v][pos] >= 1) return rets[v][pos] - 1;
long long res = 0;
for (int i = 1; i <= v; i++) {
res += ncr(v - 1, i - 1)*nr2[pos][i];
res %= mod;
}
rets[v][pos] = res + 1;
return res;
}
int main() {
cin >> N;
for (int i = 1; i <= N; i++) {
cin >> A[i] >> B[i]; B[i]++;
V.push_back(A[i]);
V.push_back(B[i]);
}
sort(V.begin(), V.end());
V.erase(unique(V.begin(), V.end()), V.end());
for (int i = 1; i <= N; i++) {
A[i] = lower_bound(V.begin(), V.end(), A[i]) - V.begin();
B[i] = lower_bound(V.begin(), V.end(), B[i]) - V.begin();
}
init();
dp[0][1] = 1;
for (int i = 0; i < V.size() - 1; i++) {
for (int j = 1; j <= N + 1; j++) {
if (dp[i][j] == 0) continue;
dp[i + 1][j] += dp[i][j]; dp[i + 1][j] %= mod;
int G = 0;
for (int k = j + 1; k <= N + 1; k++) {
if (A[k - 1] <= i && i < B[k - 1]) {
G++;
dp[i + 1][k] += dp[i][j] * solve(G, i);
dp[i + 1][k] %= mod;
}
}
}
}
long long sum = 0;
for (int i = 2; i <= N + 1; i++) sum += dp[V.size() - 1][i];
cout << sum%mod << endl;
return 0;
}
