#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);++i)
#define all(a) (a).begin(),(a).end()
#define dunk(a) cout << (a) << endl
using namespace std;
typedef long long ll;

signed int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n;
	cin >> n;
	vector<int> a(n - 1);
	vector<int> b(n - 1);
	int res1 = 0;
	int res2 = 0;
	int in = 0;
	int out = 0;
	rep(i, n - 1) {
		cin >> a[i] >> b[i];
		res1 += a[i];
		res2 += b[i];
		if (a[i] - b[i] >= 0) in += a[i] - b[i];
		else out += b[i] - a[i];
	}

	if (in == 0) {
		res1++;
		dunk(res1);
		return 0;
	}
	if (out == 0) {
		res2++;
		dunk(res2);
		return 0;
	}

	dunk(res1* res2 + 1);

	return 0;
}