#include <stdio.h>
#include <math.h>
#include <algorithm>
using namespace std;
#define MAX 250

int p[MAX][MAX];
int m[MAX][MAX];
int x[MAX];
int y[MAX];

double prunik(int p, int dx, int dy, int x0, int y0)
{
	return dx*(p-y0)/(double) dy + x0;
}

int main()
{
	int N;
	while (1)
	{
		scanf("%d", &N);
		if (N == 0)
			break;
		for (int i = 0; i < N; i++)
		{
			scanf("%d %d", &x[i], &y[i]);
			x[i] += 101;
			y[i] += 101;
		}

		x[N] = x[0];
		y[N] = y[0];
		

		for (int i = 0; i < MAX; i++)
		{
			for (int j = 0; j < MAX; j++)
			{
				p[i][j] = m[i][j] = 0;
			}
		}

		for (int i = 0; i < N; i++)
		{
			int dx = x[i] - x[i+1];
			int dy = y[i] - y[i+1];
			int x0 = min(x[i], x[i+1]);
			int y0 = x[i] < x[i+1] ? y[i] : y[i+1];
			int y1 = x[i] < x[i+1] ? y[i+1] : y[i];
			int smer = (y0 < y1) ? +1 : -1; 
			int ymin = min(y[i], y[i+1]);
			int ymax = max(y[i], y[i+1]);
			if (dx < 0)
			{
				dx *= -1;
				dy *= -1;
			}
			
			if (dy == 0)
				continue;
			if (dx == 0)
			{
				for (int j = ymin; j < ymax; j++)
				{
					p[j][x0]++;
					m[j][x0]++;
				}
				continue;
			}
			for (int j = ymin; j < ymax; j++)
			{
				double a; double b; int ra, rb;
				a = prunik(j, dx, dy, x0, y0);
				b = prunik(j+1, dx, dy, x0, y0);
				if (a - round(a) < 0.0001 && a - round(a) > -0.0001)
					a = round(a);
				if (b - round(b) < 0.0001 && b - round(b) > -0.0001)
					b = round(b);

				if (smer == 1)
				{
					ra = floor(a);
					rb = ceil(b);
					p[j][ra]++;
					m[j][rb]++;					
				}
				else
				{
					ra = ceil(a);
					rb = floor(b);					
					p[j][rb]++;
					m[j][ra]++;					
				}			
			}
		}

		/*for (int i = 90; i <= 110; i++)
		{
			for (int j = 110; j >= 90; j--)
			{
				if (p[i][j])
					printf("%d  ", p[i][j]);
				else
					printf(".  ");
			}
			printf("\n");
		}
		
		printf("\n\n");
		for (int i = 90; i <= 110; i++)
		{
			for (int j = 110; j >= 90; j--)
			{
				if (m[i][j])
					printf("%d  ", m[i][j]);
				else
					printf(".  ");
			}
			printf("\n");
		}*/

		int sum = 0;
		for (int i = 0; i < MAX; i++)
		{
			int to = 0; int done = 0;
			for (int j = 0; j < MAX; j++)
			{
				to += p[i][j];
				done += m[i][j];
				to -= m[i][j];

				if (to == 0 && done % 2 == 1)
					sum++;				
			}
		}
		printf("%d\n", sum);
	}
	return 0;
}