#include <bits/stdc++.h>
using namespace std;
const int IINF = INT_MAX;
class Point {
 public:
  double x, y;
  Point(double x = -IINF, double y = -IINF) : 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-8)) ? x < p.x : y < p.y;
  }
  bool operator==(const Point& p) const {
    return fabs(x - p.x) < (1e-8) && fabs(y - p.y) < (1e-8);
  }
};
struct Segment {
  Point p1, p2;
  Segment(Point p1 = Point(), Point p2 = Point()) : p1(p1), p2(p2) {}
  bool operator<(const Segment& s) const {
    if (!(p1 == s.p1)) return p1 < s.p1;
    return p2 < s.p2;
  }
  bool operator==(const Segment& p) const { return p.p1 == p1 && p.p2 == 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-8)) return 1;
  if (cross(a, b) < -(1e-8)) return -1;
  if (dot(a, b) < -(1e-8)) 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-8) ||
         abs(cross(l.p2 - l.p1, m.p1 - l.p1)) < (1e-8);
}
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-8);
}
bool intersectLP(Segment l, Point p) {
  return abs(cross(l.p2 - p, l.p1 - p)) < (1e-8);
}
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-8);
}
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-8) && abs(B) < (1e-8)) {
    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-8)) assert(false);
  return m.p1 + (m.p2 - m.p1) * (B / A);
}
bool isParallel(Point a, Point b) {
  return (fabs((cross(a, b)) - (0.0)) < (1e-8));
}
bool isParallel(Point a1, Point a2, Point b1, Point b2) {
  return isParallel(a1 - a2, b1 - b2);
}
bool isParallel(Segment s1, Segment s2) {
  return (fabs((cross(s1.p2 - s1.p1, s2.p2 - s2.p1)) - (0.0)) < (1e-8));
}
struct Edge {
  int from, to;
  double cost;
  Edge(int from = IINF, int to = IINF, double cost = IINF)
      : from(from), to(to), cost(cost) {}
  bool operator<(const Edge& a) const { return cost < a.cost; }
};
vector<vector<Edge> > segmentArrangement(vector<Segment> vs,
                                         vector<Point>& ps) {
  for (int i = 0; i < (int)vs.size(); i++) ps.push_back(vs[i].p1);
  for (int i = 0; i < vs.size(); i++) {
    for (int j = 0; j < vs.size(); j++)
      if (i != j && !isParallel(vs[i], vs[j]) && intersectLS(vs[i], vs[j])) {
        ps.push_back(crosspoint(vs[i], vs[j]));
      }
  }
  for (int i = 0; i < vs.size(); i++)
    for (int j = i + 1; j < vs.size(); j++)
      if (intersectSS(vs[i], vs[j]))
        ps.push_back(Point(crosspoint(vs[i], vs[j])));
  sort(ps.begin(), ps.end());
  ps.erase(unique(ps.begin(), ps.end()), ps.end());
  vector<vector<Edge> > ret(ps.size());
  for (int i = 0; i < vs.size(); i++) {
    vector<pair<double, int> > list;
    for (int j = 0; j < ps.size(); j++)
      if (intersectSP(vs[i], ps[j]))
        list.push_back(pair<double, int>(norm(vs[i].p1 - ps[j]), j));
    sort(list.begin(), list.end());
    for (int j = 0; j + 1 < list.size(); ++j) {
      int from = list[j].second, to = list[j + 1].second;
      double cost = abs(ps[from] - ps[to]);
      ret[from].push_back(Edge(from, to, cost));
      ret[to].push_back(Edge(to, from, cost));
    }
  }
  return ret;
}
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-8);
}
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-8));
}
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 (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()]);
  }
  return (fabs(sum - 2 * M_PI) < (1e-8) || fabs(sum + 2 * M_PI) < (1e-8));
}
const int MAX_N = 17;
const int MAX_SEG = 20000;
int n, bc[1 << MAX_N], trans[MAX_N];
Point input[MAX_N];
bool reachable[MAX_SEG];
vector<Point> G;
bool check(int bitmask, const vector<Segment>& segs, const vector<Point>& ps) {
  for (int i = 0; i < (int)segs.size(); i++) reachable[i] = false;
  for (int i = 0; i < n; i++) {
    if ((bitmask >> i) & 1) {
      int cur = trans[i];
      for (int j = 0; j < (int)segs.size(); j++) {
        if (segs[j].p1 == ps[cur] || segs[j].p2 == ps[cur]) {
          reachable[j] = true;
        } else {
          bool failed = false;
          Point mp = segs[j].p1;
          mp = mp - segs[j].p2;
          double dist = abs(mp);
          mp = mp / dist;
          mp = mp * (dist / 2.0) + segs[j].p2;
          Segment M = Segment(mp, ps[cur]);
          bool para = false;
          if (isParallel(M, segs[j])) para = true;
          for (int l = 0; l < (int)segs.size(); l++) {
            if (l == j) continue;
            if (ps[cur] == segs[l].p1 || ps[cur] == segs[l].p2) continue;
            if (para) {
              if (onSegment(M.p1, M.p2, segs[l].p1) ||
                  onSegment(M.p1, M.p2, segs[l].p2))
                continue;
              if (intersectSS(M, segs[l])) {
                failed = true;
                goto Skip;
              }
              continue;
            }
            if (intersectSS(M, segs[l])) {
              failed = true;
              goto Skip;
            }
          }
        Skip:;
          if (!failed && !isParallel(segs[j], M)) {
            Point centroid = M.p2;
            centroid = centroid - M.p1;
            double dist2 = abs(centroid);
            centroid = centroid / dist2;
            centroid = centroid * (dist2 / 2.0) + M.p1;
            if (!inPolygon(G, centroid)) {
              failed = true;
            }
          }
          if (!failed) reachable[j] = true;
        }
      }
    }
  }
  for (int i = 0; i < (int)segs.size(); i++)
    if (!reachable[i]) return false;
  return true;
}
int main() {
  for (int i = 0; i < (1 << MAX_N); i++) bc[i] = __builtin_popcount(i);
  while (cin >> n, n) {
    G.clear();
    assert(n <= MAX_N);
    for (int i = 0; i < n; i++) {
      cin >> input[i].x >> input[i].y;
      input[i].x += 1000, input[i].y += 1000;
      G.push_back(input[i]);
    }
    vector<Segment> segs;
    vector<Point> ps;
    for (int i = 0; i < n; i++)
      segs.push_back(Segment(input[i], input[(i + 1) % n]));
    vector<vector<Edge> > G = segmentArrangement(segs, ps);
    while (MAX_SEG <= (int)ps.size())
      ;
    vector<Segment> new_segs;
    for (int i = 0; i < G.size(); i++) {
      for (int j = 0; j < G[i].size(); j++) {
        int from = i, to = G[i][j].to;
        if (from > to) swap(from, to);
        new_segs.push_back(Segment(ps[from], ps[to]));
      }
    }
    sort(new_segs.begin(), new_segs.end());
    new_segs.erase(unique(new_segs.begin(), new_segs.end()), new_segs.end());
    for (int i = 0; i < n; i++) {
      int pos = -1;
      for (int j = 0; j < (int)ps.size(); j++)
        if (input[i] == ps[j]) {
          pos = j;
          break;
        }
      while (pos == -1)
        ;
      trans[i] = pos;
    }
    int mini = n;
    for (int i = 1; i < (1 << n); i++) {
      if (mini <= bc[i]) continue;
      if (check(i, new_segs, ps)) {
        mini = min(mini, bc[i]);
      }
    }
    cout << mini << endl;
  }
  return 0;
}
