#include <bits/stdc++.h>
using namespace std;
int n, ans, l[500005], r[500005];
pair <int, int>  a[500005];
int main () {
	cin >> n;
	for (int i = 1;i <= n;i ++) {
		cin >> l[i] >> r[i];
		a[i] = {l[i], r[i]};
	}
	sort (l + 1, l + n + 1);
	sort (r + 1, r + n + 1);
	for (int i = 1;i <= n;i ++) {
		ans += (lower_bound (r, r + n, a[i].first) - r) + l + n - upper_bound (l, l + n, a[i].second);
	}
	ans = n * (n - 1ll) / 2 - ans / 2;
	if(ans == 0) {
		cout << 0;
		return 0;
	}
	cout << ans + 1;
	return 0;
}

样例全过，悬赏一关