#include <bits/stdc++.h>
using namespace std;

#define all(x) begin(x), end(x)
#define sz(x) (ll)(x).size()

using ll = long long;
using ld = long double;
using pt = complex<ll>;

constexpr ll inf = 0x3FFFFFFFFFFF;

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

	ll n;
	cin >> n;
	ll l = inf;
	ll r = -inf;
	ll u = -inf;
	ll d = inf;
	for (ll i = 0; i < n; i++) {
		ll x, y;
		cin >> x >> y;
		pt tmp = pt(x,y)*pt(1,1);
		l = min(l, real(tmp));
		r = max(r, real(tmp));
		u = max(u, imag(tmp));
		d = min(d, imag(tmp));
	}
	ll w = r-l+1;
	ll h = u-d+1;
	ll res = (w+2)*(h+2)-h*w;
	res /= 2;
	if ((h == 1) != (w == 1)) res++;
	cout << res << endl;
}