#include<bits/stdc++.h>
using namespace std;
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcount
#define ll long long
#define mp make_pair
#define f first
#define s second
#define Time (double)clock()/CLOCKS_PER_SEC
const int N = 1007, MOD = 1000 * 1000 * 1000 + 7;
int mod(ll n) {
if (n < MOD)
return n;
else if (n < 2 * MOD)
return n - MOD;
else
return n % MOD;
}
int fp(int a, int p) {
ll ans = 1, c = a;
for (int i = 0; (1ll << i) <= p; ++i) {
if ((p >> i) & 1) ans = mod(ans * c);
c = mod(c * c);
}
return ans;
}
int dv(int a, int b) { return mod((ll)a * fp(b, MOD - 2)); }
void addmod(int &a, int b) {
a = mod(a + b);
}
int C(int n, int k) {
if (n < k)
return 0;
ll a = 1;
for (int i = n; i > n - k; --i)
a = mod(a * i);
ll b = 1;
for (int i = 1; i <= k; ++i)
b = mod(b * i);
return dv(a, b);
}
int n, l[N], r[N], dp[N][N], mem[N][N], cur[N], pref[N], lmao[N];
signed main() {
#ifdef HOME
freopen("input.txt", "r", stdin);
#else
ios_base::sync_with_stdio(0); cin.tie(0);
#endif
for (int i = 0; i < N; ++i)
mem[i][0] = 1;
for (int i = 1; i < N; ++i)
for (int j = 1; j < N; ++j)
mem[i][j] = mod(mem[i - 1][j] + mem[i - 1][j - 1]);
cin >> n;
vector <int> c;
for (int i = 1; i <= n; ++i) {
cin >> l[i] >> r[i];
c.app(l[i]); c.app(r[i] + 1);
}
sort(all(c));
c.resize(unique(all(c)) - c.begin());
dp[0][0] = 1;
for (int i = 0; i + 1 < (int)c.size(); ++i) {
for (int j = 0; j <= n; ++j)
cur[j] = C(c[i + 1] - c[i], j);
for (int j = 1; j <= n; ++j)
pref[j] = pref[j - 1] + (l[j] <= c[i] && c[i + 1] - 1 <= r[j]);
for (int mx = 1; mx <= n; ++mx) {
lmao[mx] = 0;
for (int cnt = 1; cnt <= mx; ++cnt)
addmod(lmao[mx], mod((ll)mem[mx - 1][cnt - 1] * cur[cnt]));
}
for (int j = 0; j <= n; ++j) {
addmod(dp[i + 1][j], dp[i][j]);
for (int k = j + 1; k <= n; ++k) {
if (l[k] <= c[i] && c[i + 1] - 1 <= r[k]) {
int mx = pref[k] - pref[j];
addmod(dp[i + 1][k], mod((ll)dp[i][j] * lmao[mx]));
}
}
}
}
int ans = 0;
for (int i = 1; i <= n; ++i)
addmod(ans, dp[c.size() - 1][i]);
cout << ans << '\n';
}
