#include <bits/stdc++.h>
using namespace std;
const int IINF = INT_MAX;
class Point {
 public:
  double x, y;
  Point(double x = 0, double y = 0) : x(x), y(y) {}
  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(a * x, a * y); }
  Point operator/(double a) { return Point(x / a, y / a); }
  Point operator*(Point a) {
    return Point(x * a.x - y * a.y, x * a.y + y * a.x);
  }
  bool operator<(const Point& p) const {
    return !(fabs((x) - (p.x)) < (1e-10)) ? x < p.x : y < p.y;
  }
  bool operator==(const Point& p) const {
    return fabs(x - p.x) < (1e-10) && fabs(y - p.y) < (1e-10);
  }
};
struct Segment {
  Point p1, p2;
  Segment(Point p1 = Point(), Point p2 = Point()) : p1(p1), p2(p2) {}
  bool operator==(const Segment& p) const {
    return (p.p1 == p1 && p.p2 == p2) || (p.p1 == p2 && p.p2 == p1);
  }
  bool operator<(const Segment& s) const {
    return !(p1 == s.p1) ? p1 < s.p1 : p2 < s.p2;
  }
};
ostream& operator<<(ostream& os, const Point& a) {
  os << "(" << a.x << "," << a.y << ")";
}
ostream& operator<<(ostream& os, const Segment& a) {
  os << "( " << a.p1 << " , " << a.p2 << " )";
}
double dot(Point a, Point b) { return a.x * b.x + a.y * b.y; }
double cross(Point a, Point b) { return a.x * b.y - a.y * b.x; }
double norm(Point a) { return a.x * a.x + a.y * a.y; }
double abs(Point a) { return sqrt(norm(a)); }
Point rotate(Point a, double rad) {
  return Point(cos(rad) * a.x - sin(rad) * a.y,
               sin(rad) * a.x + cos(rad) * a.y);
}
double toRad(double agl) { return agl * M_PI / 180.0; }
double getArg(Point a, Point b, Point c) {
  double arg1 = atan2(b.y - a.y, b.x - a.x);
  double arg2 = atan2(c.y - b.y, c.x - b.x);
  double arg = fabs(arg1 - arg2);
  while (arg > M_PI) arg -= 2.0 * M_PI;
  return fabs(arg);
}
int ccw(Point p0, Point p1, Point p2) {
  Point a = p1 - p0;
  Point b = p2 - p0;
  if (cross(a, b) > (1e-10)) return 1;
  if (cross(a, b) < -(1e-10)) return -1;
  if (dot(a, b) < -(1e-10)) return 2;
  if (norm(a) < norm(b)) return -2;
  return 0;
}
bool intersectLL(Segment l, Segment m) {
  return abs(cross(l.p2 - l.p1, m.p2 - m.p1)) > (1e-10) ||
         abs(cross(l.p2 - l.p1, m.p1 - l.p1)) < (1e-10);
}
bool intersectLS(Segment l, Segment s) {
  return cross(l.p2 - l.p1, s.p1 - l.p1) * cross(l.p2 - l.p1, s.p2 - l.p1) <
         (1e-10);
}
bool intersectLP(Segment l, Point p) {
  return abs(cross(l.p2 - p, l.p1 - p)) < (1e-10);
}
bool intersectSS(Segment s, Segment t) {
  return ccw(s.p1, s.p2, t.p1) * ccw(s.p1, s.p2, t.p2) <= 0 &&
         ccw(t.p1, t.p2, s.p1) * ccw(t.p1, t.p2, s.p2) <= 0;
}
bool intersectSP(Segment s, Point p) {
  return abs(s.p1 - p) + abs(s.p2 - p) - abs(s.p2 - s.p1) < (1e-10);
}
Point projection(Segment l, Point p) {
  double t = dot(p - l.p1, l.p1 - l.p2) / norm(l.p1 - l.p2);
  return l.p1 + (l.p1 - l.p2) * t;
}
Point reflection(Segment l, Point p) { return p + (projection(l, p) - p) * 2; }
double distanceLP(Segment l, Point p) { return abs(p - projection(l, p)); }
double distanceLL(Segment l, Segment m) {
  return intersectLL(l, m) ? 0 : distanceLP(l, m.p1);
}
double distanceLS(Segment l, Segment s) {
  if (intersectLS(l, s)) return 0;
  return min(distanceLP(l, s.p1), distanceLP(l, s.p2));
}
double distanceSP(Segment s, Point p) {
  Point r = projection(s, p);
  if (intersectSP(s, r)) return abs(r - p);
  return min(abs(s.p1 - p), abs(s.p2 - p));
}
double distanceSS(Segment s, Segment t) {
  if (intersectSS(s, t)) return 0;
  return min(min(distanceSP(s, t.p1), distanceSP(s, t.p2)),
             min(distanceSP(t, s.p1), distanceSP(t, s.p2)));
}
Point crosspoint(Segment l, Segment m) {
  double A = cross(l.p2 - l.p1, m.p2 - m.p1);
  double B = cross(l.p2 - l.p1, l.p2 - m.p1);
  if (abs(A) < (1e-10) && abs(B) < (1e-10)) {
    vector<Point> vec;
    vec.push_back(l.p1), vec.push_back(l.p2), vec.push_back(m.p1),
        vec.push_back(m.p2);
    sort(vec.begin(), vec.end());
    assert(vec[1] == vec[2]);
    return vec[1];
  }
  if (abs(A) < (1e-10)) assert(false);
  return m.p1 + (m.p2 - m.p1) * (B / A);
}
double cross3p(Point p, Point q, Point r) {
  return (r.x - q.x) * (p.y - q.y) - (r.y - q.y) * (p.x - q.x);
}
bool collinear(Point p, Point q, Point r) {
  return fabs(cross3p(p, q, r)) < (1e-10);
}
bool ccwtest(Point p, Point q, Point r) { return cross3p(p, q, r) > 0; }
bool onSegment(Point p, Point q, Point r) {
  return collinear(p, q, r) &&
         (fabs((sqrt(pow(p.x - r.x, 2) + pow(p.y - r.y, 2)) +
                sqrt(pow(r.x - q.x, 2) + pow(r.y - q.y, 2))) -
               (sqrt(pow(p.x - q.x, 2) + pow(p.y - q.y, 2)))) < (1e-10));
}
bool isConvex(vector<Point> p) {
  int sz = (int)p.size();
  if (sz < 3) return false;
  bool isLeft = ccwtest(p[0], p[1], p[2]);
  for (int i = 1; i < (int)p.size(); i++)
    if (ccwtest(p[i], p[(i + 1) % sz], p[(i + 2) % sz]) != isLeft) return false;
  return true;
}
double angle(Point a, Point b, Point c) {
  double ux = b.x - a.x, uy = b.y - a.y;
  double vx = c.x - a.x, vy = c.y - a.y;
  return acos((ux * vx + uy * vy) /
              sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy)));
}
bool inPolygon(vector<Point> poly, Point p) {
  if ((int)poly.size() == 0) return false;
  for (int i = 0; i < poly.size(); i++)
    if (onSegment(poly[i], poly[(i + 1) % poly.size()], p)) return true;
  double sum = 0;
  for (int i = 0; i < (int)poly.size(); i++) {
    if ((fabs((cross(poly[i] - p, poly[(i + 1) % poly.size()] - p)) - (0.0)) <
         (1e-10)))
      continue;
    if (cross3p(p, poly[i], poly[(i + 1) % poly.size()]) < 0)
      sum -= angle(p, poly[i], poly[(i + 1) % poly.size()]);
    else
      sum += angle(p, poly[i], poly[(i + 1) % poly.size()]);
  }
  const double eps = 1e-5;
  return (fabs(sum - 2 * M_PI) < eps || fabs(sum + 2 * M_PI) < eps);
}
bool inPolygon(const vector<Point>& poly, Segment seg) {
  vector<Point> vp;
  vp.push_back(seg.p1);
  vp.push_back(seg.p2);
  for (int i = 0; i < (int)poly.size(); i++) {
    Segment edge = Segment(poly[i], poly[(i + 1) % (int)poly.size()]);
    if ((fabs((cross(seg.p1 - seg.p2, edge.p1 - edge.p2)) - (0.0)) < (1e-10))) {
      if (onSegment(seg.p1, seg.p2, edge.p1)) vp.push_back(edge.p1);
      if (onSegment(seg.p1, seg.p2, edge.p2)) vp.push_back(edge.p2);
    } else {
      if (intersectSS(seg, edge)) vp.push_back(crosspoint(seg, edge));
    }
  }
  sort(vp.begin(), vp.end());
  vp.erase(unique(vp.begin(), vp.end()), vp.end());
  for (int i = 0; i < (int)vp.size() - 1; i++) {
    Point middle_point = (vp[i] + vp[i + 1]) / 2.0;
    if (!inPolygon(poly, middle_point)) return false;
  }
  return true;
}
const int MAX_V = 16 * 20;
int n, bc[1 << 16];
Point ps[16];
vector<Point> poly;
bool saw[MAX_V];
vector<Segment> segs;
bool check(int bitmask) {
  int V = segs.size();
  assert(V < MAX_V);
  for (int i = 0; i < V; i++) saw[i] = false;
  for (int i = 0; i < n; i++)
    if ((bitmask >> i) & 1) {
      saw[i] = saw[(i - 1 + n) % n] = true;
      Point sp = ps[i];
      for (int j = 0; j < V; j++)
        if (!saw[j]) {
          Point mp = (segs[j].p1 + segs[j].p2) / 2.0;
          Segment seg = Segment(sp, mp);
          if (!inPolygon(poly, seg)) continue;
          bool failed = false;
          for (int k = 0; k < V; k++) {
            if (intersectSS(seg, segs[k])) {
              if (onSegment(segs[k].p1, segs[k].p2, seg.p1) ||
                  onSegment(segs[k].p1, segs[k].p2, seg.p2))
                continue;
              failed = true;
              break;
            }
          }
          seg = Segment(sp, segs[j].p1);
          for (int k = 0; k < V; k++) {
            if (intersectSS(seg, segs[k])) {
              if (onSegment(segs[k].p1, segs[k].p2, seg.p1) ||
                  onSegment(segs[k].p1, segs[k].p2, seg.p2))
                continue;
              failed = true;
              break;
            }
          }
          seg = Segment(sp, segs[j].p2);
          for (int k = 0; k < V; k++) {
            if (intersectSS(seg, segs[k])) {
              if (onSegment(segs[k].p1, segs[k].p2, seg.p1) ||
                  onSegment(segs[k].p1, segs[k].p2, seg.p2))
                continue;
              failed = true;
              break;
            }
          }
          if (!failed) saw[j] = true;
        }
    }
  for (int i = 0; i < V; i++)
    if (!saw[i]) return false;
  return true;
}
Point vir;
bool comp(const Point& p1, const Point& p2) {
  return abs(vir - p1) < abs(vir - p2);
}
vector<Segment> makeGraph() {
  vector<Segment> vs;
  for (int i = 0; i < n; i++) vs.push_back(Segment(ps[i], ps[(i + 1) % n]));
  vector<Segment> ret;
  for (int i = 0; i < vs.size(); i++) {
    vector<Point> vp;
    vp.push_back(vs[i].p1);
    vp.push_back(vs[i].p2);
    for (int j = 0; j < vs.size(); j++) {
      if (onSegment(vs[i].p1, vs[i].p2, vs[j].p1) ||
          onSegment(vs[i].p1, vs[i].p2, vs[j].p2))
        continue;
      if ((fabs((cross(vs[i].p1 - vs[i].p2, vs[j].p1 - vs[j].p2)) - (0.0)) <
           (1e-10)))
        continue;
      if (intersectLS(vs[j], vs[i])) vp.push_back(crosspoint(vs[i], vs[j]));
    }
    vir = vs[i].p1;
    sort(vp.begin(), vp.end(), comp);
    vp.erase(unique(vp.begin(), vp.end()), vp.end());
    for (int j = 0; j < (int)vp.size() - 1; j++)
      ret.push_back(Segment(vp[j], vp[j + 1]));
  }
  return ret;
}
int main() {
  for (int i = 0; i < 1 << 16; i++) bc[i] = __builtin_popcount(i);
  while (cin >> n, n) {
    for (int i = 0; i < n; i++) cin >> ps[i].x >> ps[i].y;
    poly.resize(n);
    for (int i = 0; i < n; i++) poly[i] = ps[i];
    segs = makeGraph();
    int ans = n;
    for (int i = 0; i < (1 << n); i++) {
      if (bc[i] >= ans) continue;
      if (check(i)) ans = min(ans, bc[i]);
    }
    cout << ans << endl;
  }
  return 0;
}
