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#include <bits/stdc++.h>
#define LLINF 100000000000000007

using namespace std;
typedef long long ll;
typedef string str;
template <typename T> using vec = vector<T>;

const ll MOD = 1e9 + 7;
// const ll MOD2 = 1000992299;

ll powm(ll a, ll n);
ll multm(ll a, ll b);
ll divm(ll a, ll b);
ll n, N;
// {age, v}
vec<int> seg_tree;
vec<vec<int>> tG;
vec<ll> facts;

void init();
void prep_factorials();
void change_on_range(int cur, int left, int right, int lOb, int rOb, int v) {
	if(left == lOb && right == rOb) {
		seg_tree[cur] = v;
		return;
	}
	int mid = (lOb + rOb) / 2;
	if(right <= mid) return change_on_range(cur * 2, left, right, lOb, mid, v);
	if(left > mid) return change_on_range(cur * 2 + 1, left, right, mid + 1, rOb, v);

	change_on_range(cur * 2, left, mid, lOb, mid, v);
	change_on_range(cur * 2 + 1, mid + 1, right, mid + 1, rOb, v);
}

int get_latest_node(int v) {
	v += N - 1;
	int node = 0;
	while(v > 0) {
		node = max(node, seg_tree[v]);
		v /= 2;
	}
	return node;
}


ll mult_ft(ll from, ll to) {
	return divm(facts[to], facts[from - 1]);
}

ll combs_heura(ll on_right) {
	ll frow = multm(mult_ft(1, n - on_right - 1), mult_ft(1, on_right));
	return divm(multm(frow, mult_ft(on_right + 2, n)), mult_ft(1, (n - on_right - 1)));
}

int bfs_count(int s) {
	const int LIM = 5 * 1e5 + 7;
	queue<int> q;
	bitset<LIM> vis;
	q.push(s);
	vis[s] = true;
	int count = 0;

	while(!q.empty()) {
		int v = q.front();
		q.pop();
		for(auto e : tG[v]) {
			if(vis[e]) continue;
			q.push(e);
			count++;
			vis[e] = true;
		}
	}
	return count;
}


int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);

	cin>>n;
	init();
	prep_factorials();
	for(int i = 1; i <= n; i++) {
		int l, r;
		cin>>l>>r;
		int gl = get_latest_node(l);
		int gr = get_latest_node(r);

		// cout<<"i: "<<i<<"\n";
		// cout<<"(gr, gl): ("<<gr<<","<<gl<<")\n";
		if(gl == gr) tG[gl].push_back(i);
		else {
			tG[gl].push_back(i);
			tG[gr].push_back(i);
		}
		change_on_range(1, l, r, 1, N, i);
	}

	ll wyn = 0;
	for(int i = 1; i <= n; i++) {
		ll c = bfs_count(i);
		// cout<<"c: "<<c<<"\n";
		// cout<<"ch(c): "<<combs_heura(c)<<"\n";
		wyn = (wyn + combs_heura(c)) % MOD;
	}

	cout<<divm(wyn, facts[n]);

	cout.flush();
	return 0;
}

void init() {
	tG = vec<vec<int>>(n + 1);
	N = 1;
	while(N < 2 * n) N *= 2;
	seg_tree = vec<int>(2 * N, 0);
}


void prep_factorials() {
	facts = vec<ll>(n + 7);
	facts[0] = 1;
	for(ll i = 1; i < n + 7; i++) facts[i] = multm(facts[i - 1], i);
}







ll powm(ll a, ll n) {
  ll w = 1;

  while (n > 0) {
    if (n % 2 == 1)
      w = (w * a) % MOD;
      a = (a * a) % MOD;
      n /= 2;
  }
  return w;
}

ll multm(ll a, ll b) {
  return (a * b) % MOD;
}

ll divm(ll a, ll b) {
  return multm(a, powm(b, MOD - 2));
}