#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <ll, ll> pii;
const int N = 505;
const int M = 1005;
const int MOD = 1e9 + 7;
int n, m;
ll a[N], b[N];
ll dp[N][M];
vector <pii> v;
ll x[M], y[M];
vector <int> z[M];
int sz[M];
ll wide[M];
int counter = 1;
ll comb[M][N];
ll inverse[N];
ll bigMod (ll a, ll e) {
if (e == -1) e = MOD - 2;
ll r = 1ll; while (e) {
if (e & 1) r = (r * a) % MOD;
a = (a * a) % MOD;
e >>= 1;
}
return r;
}
ll call (int at, int range) {
if (at > n or range > m) return 1;
if (dp[at][range] != -1) return dp[at][range];
int pos = 0;
while (pos < sz[range] and z[range][pos] < at) {
++pos;
}
ll ret = call(at, range + 1);
for (int i = pos; i < sz[range]; ++i) {
int rem = i - pos, cur = z[range][i];
// cout << rem << " comb ---> " << comb[range][rem] << endl;
ll add = (comb[range][rem] * call(cur + 1, range + 1)) % MOD;
ret += add, ret %= MOD;
}
return dp[at][range] = ret;
}
ll nCr (ll n, ll r) {
if (n < r or n < 0 or r < 0) return 0;
ll res = 1ll;
for (ll i = n; i >= n - r + 1; --i) {
res *= i, res %= MOD;
}
for (ll i = 1; i <= r; ++i) {
res *= inverse[i];
res %= MOD;
}
return res;
}
int main (int argc, char const *argv[]) {
scanf("%d", &n);
for (int i = 1; i <= n; ++i) {
scanf("%lld %lld", a + i, b + i);
v.push_back({a[i], 0});
v.push_back({b[i], 1});
}
sort(v.begin(), v.end());
for (int i = 1; i < n + n; ++i) {
int one = v[i - 1].second, two = v[i].second;
int l = v[i - 1].first, r = v[i].first;
if (!one and !two) {
--r, ++counter;
if (l <= r) x[++m] = l, y[m] = r;
} else if (!one and two) {
--counter;
// cout << "yo " << i << " " << m << endl;
if (l <= r) x[++m] = l, y[m] = r;
} else if (one and two) {
++l, --counter;
if (l <= r) x[++m] = l, y[m] = r;
} else {
++l;
if (counter and l <= r) x[++m] = l, y[m] = r;
++counter;
}
}
// cout << m << endl;
// for (int i = 1; i <= m; ++i) {
// cout << x[i] << " " << y[i] << endl;
// }
for (int i = 1; i <= m; ++i) {
for (int j = 1; j <= n; ++j) {
if (a[j] <= x[i] and y[i] <= b[j]) {
z[i].push_back(j);
++sz[i];
}
}
wide[i] = y[i] - x[i] + 1;
}
for (int i = 1; i < N; ++i) {
inverse[i] = bigMod(i, -1);
}
for (int i = 1; i <= m; ++i) {
for (int j = 0; j <= n; ++j) {
comb[i][j] = nCr(wide[i] + j, j + 1);
}
}
// for (int i = 1; i <= m; ++i) {
// cout << i << " --> ";
// for (int j : z[i]) cout << j << " ";
// cout << endl;
// }
memset(dp, -1, sizeof dp);
// for (int i = 1; i <= n; ++i) {
// for (int j = 1; j <= m; ++j) {
// cout << "(" << i << ", " << j << ") ---> " << call(i, j) << endl;
// }
// }
ll ans = call(1, 1) + MOD - 1;
printf("%lld\n", ans % MOD);
return 0;
}
