#include <cstdio>
#include <cmath>
#include <cstdlib>

int _field[300][300];

#define field(x,y) _field[(x)-150][(y)-150]
#define i_n ((i + 1) % N)

int _hrany[150][4];

#define hranax1(x) _hrany[x][0]
#define hranax2(x) _hrany[x][1]
#define hranay1(x) _hrany[x][2]
#define hranay2(x) _hrany[x][3]

typedef struct item {
	float x;
	int pm;
} item_t;

item_t tok[300];
int toks;
int tmp1, tmp2, tmp3;
double ftmp1, ftmp2, ftmp3;
int fields, checkin;

static int tokcmp(const void *a, const void *b);

int main()
{
	int N;
	int i, j, k;

	int proch;
	int seen;

	scanf("%d", &N);

	int p_x, p_y;
	int l_x, l_y;
	while (N != 0)
	{
		fields = 0;
		scanf("%d %d", &p_x, &p_y);
		for (i=1;i<N;i++)
		{
			l_x = p_x;
			l_y = p_y;
			scanf("%d %d", &p_x, &p_y);
			hranax1(i) = l_x;
			hranay1(i) = l_y;
			hranax2(i) = p_x;
			hranay2(i) = p_y;
		}
		hranax1(0) = p_x;
		hranay1(0) = p_y;
		hranax2(0) = hranax1(1);
		hranay2(0) = hranay1(1);
		for (i=0;i<N;i++)
		{
			if (hranay1(i) > hranay2(i))
			{
				tmp1 = hranax1(i);
				hranax1(i) = hranax2(i);
				hranax2(i) = tmp1;
				tmp1 = hranay1(i);
				hranay1(i) = hranay2(i);
				hranay2(i) = tmp1;
			}
		}
		
		// projdu vsechny radky
		for (i=-105;i<105;i++)
		{
			toks = 0;
			// pro vsechny hrany
			for (j=0; j<N;j++)
			{
#define x1	hranax1(j)
#define y1	hranay1(j)
#define x2	hranax2(j)
#define y2	hranay2(j)
#define add(lx,lpm) do { tok[toks].x = lx; tok[toks].pm = lpm; toks++; } while (0)
				// protina tato hrana pas y: (i, i+1) ?
				if (y1 > i) continue;
				if (y2 < i+1) continue;
				
				ftmp1 = x1 + (i - y1) * (x2 - x1)/((double) y2 - y1);
				ftmp2 = x1 + (i + 1 - y1) * (x2 - x1)/((double) y2 - y1);
				if (ftmp1 > ftmp2)
				{
					ftmp3 = ftmp1;
					ftmp1 = ftmp2;
					ftmp2 = ftmp3;
				}
				ftmp1 = floor(ftmp1);
				ftmp2 = ceil(ftmp2);
				if (ftmp1 == ftmp2) add(ftmp1, 42);
				else
					{
						add (ftmp1, 1);
						add (ftmp2, -1);
					}
//				printf("r%d u%d: %lf -> %lf\n", i, j, ftmp1, ftmp2);
#undef x1
#undef y1
#undef x2
#undef y2
			}
			qsort(tok, toks, sizeof (item_t), tokcmp);
			j = 0;
			seen = 0;
			proch = 0;
			for (k=-105; k< 105; k++)
			{
				while (j < toks && tok[j].x == k)
				{
					switch (tok[j].pm)
					{
						case 1: proch++;
							seen++;
							break;
						case -1: proch--;
							 break;
						case 42: seen++;
							 break;
					}
					j++;
				}
	//			printf("%d %d\n", seen, proch);
				if ((seen % 2 == 1) && (proch == 0))
					fields++;
			}
		}
		printf("%d\n", fields);
		scanf("%d", &N);
	}
	
} 

static int tokcmp(const void *a, const void *b)
{
	return ((item_t *) a)->x - ((item_t *) b)->x;
}