#include <stdio.h>

typedef struct _pair_r {
  int s, e;
} pair_t;
int n_pair[4000];
pair_t pair[4000][500];

typedef struct _point_t {
  int x, y;
} point_t;

typedef struct _line_t {
  point_t p1, p2;
} line_t;

typedef struct _poly_t {
  point_t p[128];
  int n;
} poly_t;

int ccw(point_t p0, point_t p1, point_t p2)
{
  int dx1, dx2, dy1, dy2;
  dx1 = p1.x - p0.x;   dy1 = p1.y - p0.y;
  dx2 = p2.x - p0.x;   dy2 = p2.y - p0.y;
  if (dx1*dy2 > dy1*dx2) return +1;
  if (dx1*dy2 < dy1*dx2) return -1;
  if ((dx1*dx2 < 0) || (dy1*dy2) < 0) return -2;
  if ((dx1*dx1+dy1*dy1) < (dx2*dx2+dy2*dy2)) return +2;
  return 0;
}

int intersect(line_t l1, line_t l2)
{
  return (((ccw(l1.p1,l1.p2,l2.p1) * ccw(l1.p1,l1.p2,l2.p2)) <= 0) &&
	  ((ccw(l2.p1,l2.p2,l1.p1) * ccw(l2.p1,l2.p2,l1.p2)) <= 0));
}

int intersect2(line_t l1, line_t l2)
{
  return (((ccw(l1.p1,l1.p2,l2.p1) * ccw(l1.p1,l1.p2,l2.p2)) == -1) &&
	  ((ccw(l2.p1,l2.p2,l1.p1) * ccw(l2.p1,l2.p2,l1.p2)) == -1));
}

int inside(point_t t, poly_t p)
{
  int i, count = 0, j = 0;
  line_t lt, lp;

  p.p[p.n] = p.p[0]; p.p[p.n+1] = p.p[1];p.p[p.n+2] = p.p[2];
  lt.p1 = t; lt.p2 = t; lt.p2.x = 5000;

  for (i = 0; i < p.n; i++) {
    if (ccw(p.p[i], p.p[i+1], t) % 2 == 0) { return 0; }
  }

  if (ccw(lt.p1, lt.p2, p.p[0]) == 0) {
  for (i = 2; i <= p.n+1; i++) {
    lp.p1 = p.p[i]; lp.p2 = p.p[i];
    if (ccw(lt.p1, lt.p2, p.p[i]) != 0) {
      if (i == j+1) {
	lp.p2 = p.p[j];
	if (intersect(lp,lt)) { count++; }
      }
      else {
	if (ccw(lt.p1, lt.p2, p.p[i]) *
	    ccw(lt.p1, lt.p2, p.p[j]) < 0) { count++; }
      }
      j = i;
    }
  }
    
  return count&1;
  }

  for (i = 1; i <= p.n; i++) {
    lp.p1 = p.p[i]; lp.p2 = p.p[i];
    if (ccw(lt.p1, lt.p2, p.p[i]) != 0) {
      if (i == j+1) {
	lp.p2 = p.p[j];
	if (intersect(lp,lt)) { count++; }
      }
      else {
	if (ccw(lt.p1, lt.p2, p.p[i]) *
	    ccw(lt.p1, lt.p2, p.p[j]) < 0) { count++; }
      }
      j = i;
    }
  }
  return count & 1;
}

int complete(int x, int y, poly_t p)
{
  int dx, dy;
  point_t t;
  for (dy = 0; dy < 2; dy++) {
    for (dx = 0; dx < 2; dx++) {
      t.x = x+dx*2; t.y = y+dy*2;
      if (inside(t, p)) { return 1; }
    }
  }
  return 0;
}

int cross(int x, int y, poly_t p)
{
  int dx[5] = {0,2,2,0,0};
  int dy[5] = {0,0,2,2,0};
  int l, i;
  line_t l1, l2;

  p.p[p.n] = p.p[0]; p.p[p.n+1] = p.p[1];
  for (l = 0; l < p.n; l++) {
    for (i = 0; i < 4; i++) {
      
      l1.p1.x = x+dx[i]; l1.p1.y = y+dy[i];
      l1.p2.x = x+dx[i+1]; l1.p2.y = y+dy[i+1];
      
      l2.p1 = p.p[l]; l2.p2 = p.p[l+1];
      if (intersect2(l1, l2)) { return 1; }
    }
  }
  return 0;
}

int naname(int x, int y, poly_t p)
{
  point_t s, t;
  int l, i;

  p.p[p.n] = p.p[0]; p.p[p.n+1] = p.p[1];
  s.x = x; s.y = y;
  t.x = x+2; t.y = y+2;
  for (l = 0; l < p.n; l++) {
    if (ccw(p.p[l], p.p[l+1], s) == 0 &&
	ccw(p.p[l], p.p[l+1], t) == 0) {
      return 1;
    }
  }

  s.x = x+2; s.y = y;
  t.x = x; t.y = y+2;
  for (l = 0; l < p.n; l++) {
    if (ccw(p.p[l], p.p[l+1], s) == 0 &&
	ccw(p.p[l], p.p[l+1], t) == 0) {
      return 1;
    }
  }

  return 0;
}

int center(int x, int y, poly_t p)
{
  point_t t;

  t.x = x+1; t.y = y+1;
  if (inside(t, p)) { return 1; }
  return 0;
}

int main()
{
  int i, n, x, y, maxx, maxy, minx, miny, done;
  poly_t p;
  point_t t, h;
  int sum;

  freopen("area.txt", "r", stdin);

  while (1) {
    scanf("%d", &p.n); if (p.n == 0) break;

    maxx = maxy = -4000;
    minx = miny = 4000;

    for (i = 0; i < p.n; i++) {
      scanf("%d %d", &(p.p[i].x), &(p.p[i].y));
      p.p[i].x *= 2;
      p.p[i].y *= 2;
      if (maxx < p.p[i].x) maxx = p.p[i].x;
      if (minx > p.p[i].x) minx = p.p[i].x;
      if (maxy < p.p[i].y) maxy = p.p[i].y;
      if (miny > p.p[i].y) miny = p.p[i].y;
    }

    sum = 0;
    for (t.y = maxy + 2; t.y >= miny - 2; t.y-=2) {
      for (t.x = minx - 2; t.x <= maxx + 2; t.x+=2) {
	if (complete(t.x, t.y, p) ||
	    cross(t.x, t.y, p) ||
	    naname(t.x, t.y, p) ||
	    center(t.x, t.y, p)) { sum++; }
      }
    }
    printf("%d\n", sum);

  }
  return 0;
}