//
//  Solution Program for Problem C of Aizu 2003
//                                   written by IZUMI Yusuke <y@yuizumi.net>
//

#include <iostream>
#include <fstream>
#include <deque>
#include <utility>
#include <algorithm>

using namespace std;

deque< pair<int,int> > range[4000];

void add_edge(int px, int py, int qx, int qy)
{
	int dx = qx - px, dy = qy - py;
	if(dx < 0) { dx = -dx, dy = -dy; }
	for(int x = min(px,qx); x < max(px,qx); x++) {
		int y1 = dy * (x - px) + dx * py;
		int y2 = dy * (x+1 - px) + dx * py;
		if(y1 > y2) swap(y1, y2);
		y1 = (y1 < 0 ? y1 - dx + 1 : y1) / dx;
		y2 = (y2 < 0 ? y2 : y2 + dx - 1) / dx;
		range[x+2000].push_back(make_pair(y1, y2));
	}
}

int main(void)
{
	ifstream cin("area.txt");

	int n;
	while(cin >> n) {
		if(n == 0) break;

		// input
		int px, py, qx, qy, sx, sy;
		cin >> sx >> sy;
		px = sx, py = sy;
		for(int i = 1; i < n; i++) {
			cin >> qx >> qy;
			add_edge(px, py, qx, qy);
			px = qx, py = qy;
		}
		add_edge(px, py, sx, sy);

		// computation
		int S = 0;
		for(int x = 0; x < 4000; x++) {
			sort(range[x].begin(), range[x].end());
			int th = -2000;		// threshold
			for(int i = 0; i < range[x].size(); i += 2) {
				S += range[x][i+1].second - max(th, range[x][i].first);
				th = range[x][i+1].second;
			}
			range[x].clear();
		}

		// output
		cout << S << endl;
	}

	return 0;
}