#include<bits/stdc++.h>
 
#define REP(i,s,n) for(int i=s;i<n;i++)
#define rep(i,n) REP(i,0,n)
#define EPS (1e-8)
#define COUNTER_CLOCKWISE 1
#define CLOCKWISE -1 
#define ONLINE_BACK 2
#define ONLINE_FRONT -2
#define ON_SEGMENT 0
#define equals(a,b) (fabs((a)-(b)) < EPS)
 
using namespace std;
 
const int IINF = INT_MAX;
 
// template - begin
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 !equals(x,p.x)?x<p.x:(!equals(y,p.y)&&y<p.y); }
 
  bool operator == (const Point& p)const{ return fabs(x-p.x) < EPS && fabs(y-p.y) < EPS; }
 
};
 
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; }
};
 
typedef Point Vector;
typedef Segment Line;
typedef vector<Point> Polygon;
 
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)); }
 
//rad は角度をラジアンで持たせること
Point rotate(Point a,double rad){ return Point(cos(rad)*a.x - sin(rad)*a.y,sin(rad)*a.x + cos(rad)*a.y); }
 
// 度をラジアンに変換
double toRad(double agl){ return agl*M_PI/180.0; }
 
// a => prev, b => cur, c=> next
// prev から cur へ行って next へ行く際の角度を求める
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);
}
// template - end
 
// ccw - begin
int ccw(Point p0,Point p1,Point p2){
  Point a = p1-p0;
  Point b = p2-p0;
  if(cross(a,b) > EPS)return COUNTER_CLOCKWISE;
  if(cross(a,b) < -EPS)return CLOCKWISE;
  if(dot(a,b) < -EPS)return ONLINE_BACK;
  if(norm(a) < norm(b))return ONLINE_FRONT;
  return ON_SEGMENT;
}
// ccw - end
 
// intersect - begin
bool intersectLL(Line l, Line m) {
  return abs(cross(l.p2-l.p1, m.p2-m.p1)) > EPS || // non-parallel
         abs(cross(l.p2-l.p1, m.p1-l.p1)) < EPS;   // same line
}
bool intersectLS(Line l, Line s) {
  return cross(l.p2-l.p1, s.p1-l.p1)*       // s[0] is left of l
         cross(l.p2-l.p1, s.p2-l.p1) < EPS; // s[1] is right of l
}
bool intersectLP(Line l,Point p) {
  return abs(cross(l.p2-p, l.p1-p)) < EPS;
}
bool intersectSS(Line s, Line 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(Line s, Point p) {
  return abs(s.p1-p)+abs(s.p2-p)-abs(s.p2-s.p1) < EPS; // triangle inequality
}
 
Point projection(Line 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(Line l,Point p) {
  return p + (projection(l, p) - p) * 2;
}
double distanceLP(Line l, Point p) {
  return abs(p - projection(l, p));
}
double distanceLL(Line l, Line m) {
  return intersectLL(l, m) ? 0 : distanceLP(l, m.p1);
}
 
double distanceLS(Line l, Line s) {
  if (intersectLS(l, s)) return 0;
  return min(distanceLP(l, s.p1), distanceLP(l, s.p2));
}
double distanceSP(Line 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(Line s, Line 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(Line l,Line 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) < EPS && abs(B) < EPS){
    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]); //同じセグメントかもよ
    return vec[1];
    //return m.p1;
  }
  if(abs(A) < EPS)assert(false);
  return m.p1 + (m.p2-m.p1)*(B/A);
}
 
// intersect - end
 
// inPolygonP - begin
//cross product of pq and pr
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);
}
   
//returns true if point r is on the same line as the line pq
bool collinear(Point p,Point q,Point r)
{
  return fabs(cross3p(p,q,r)) < EPS;
}
   
//returns true if point t is on the left side of line pq
bool ccwtest(Point p,Point q,Point r)
{
  return cross3p(p,q,r) > 0;//can be modified to accept collinear points
}
  
bool onSegment(Point p,Point q,Point r)
{
  return collinear(p,q,r) && equals(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)) ) ;
}
   
 
bool isConvex(vector<Point> p)
{
  int sz = (int)p.size();
   
  if(sz < 3)return false;//boundary case, we treat a point or a line as not convex
   
  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)));
}  
   
//多角形poly内（線分上も含む）に点pが存在するかどうは判定する  
bool inPolygon(Polygon poly,Point p)
{
  if((int)poly.size() == 0)return false;
  rep(i,poly.size())
    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( equals(cross(poly[i]-p,poly[(i+1)%poly.size()]-p),0.0) ) continue; // ３点が平行だとangleがnanを返しsumがnanになり死ぬ
      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()]);
    }
  // あまり誤差を厳しくしすぎると良くないので以下のほうが良い 
  const double eps = 1e-5;
  return (fabs(sum - 2*M_PI) < eps || fabs(sum + 2*M_PI) < eps);
}  
// inPolygonP - end
 
// inPolygonS - begin
bool inPolygon(const Polygon &poly,Segment seg){
  vector<Point> vp;
  vp.push_back(seg.p1);
  vp.push_back(seg.p2);
  rep(i,(int)poly.size()) {
    Segment edge = Segment(poly[i],poly[(i+1)%(int)poly.size()]);
    if( equals(cross(seg.p1-seg.p2,edge.p1-edge.p2),0.0) ) {
      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());
  rep(i,(int)vp.size()-1) {
    Point middle_point = ( vp[i] + vp[i+1] ) / 2.0;
    if( !inPolygon(poly,middle_point) ) return false;
  }
  return true;  
}
// inPolygonS - end
 
const int MAX_V = 16 * 20+2000;
int n,bc[1<<16];
Point ps[16];
Polygon poly;
vector<Segment> segs;
 
bool check(int bitmask){
  int V = segs.size();
  assert( V < MAX_V );
  vector<Point> sp;
  rep(i,n) if( (bitmask>>i) & 1 ) sp.push_back(ps[i]);
  rep(i,V){
    Point mp = ( segs[i].p1 + segs[i].p2 ) / 2.0;
    bool ok = false;
    rep(j,bc[bitmask]){
      Segment seg = Segment(sp[j],mp);
      Point middle = ( seg.p1 + seg.p2 ) / 2.0;
      if( !inPolygon(poly,middle) ) continue;
      //if( !inPolygon(poly,seg) ) continue;
      bool failed = false;
      rep(k,n) {
        if( equals(cross(seg.p1-seg.p2,poly[k]-poly[(k+1)%n]),0.0) ) continue;
        if( intersectSS(seg,Segment(poly[k],poly[(k+1)%n])) ){
          if( onSegment(poly[k],poly[(k+1)%n],seg.p1) || onSegment(poly[k],poly[(k+1)%n],seg.p2) ) continue;
          if( onSegment(seg.p1,seg.p2,poly[k]) || onSegment(seg.p1,seg.p2,poly[(k+1)%n]) ) continue;
          failed = true;
          break;
        } 
      }
      if( !failed ) { ok = true; break; }
    }
    if( !ok ) return false;
  }

  return true;
}
 
Point vir;
bool comp(const Point& p1,const Point& p2){ return !equals(abs(vir-p1),abs(vir-p2)) && abs(vir-p1) < abs(vir-p2); }
 
vector<Segment> makeGraph(){
  vector<Segment> vs;
  rep(i,n) vs.push_back(Segment(ps[i],ps[(i+1)%n]));
  vector<Segment> ret;
  rep(i,vs.size()){
    vector<Point> vp;
    vp.push_back(vs[i].p1);
    vp.push_back(vs[i].p2);
    rep(j,n) REP(k,j+1,n) {
      Segment seg = Segment(ps[j],ps[k]);
      if( equals(cross(vs[i].p1-vs[i].p2,seg.p1-seg.p2),0.0) ) {
        if( onSegment(vs[i].p1,vs[i].p2,seg.p1) ) vp.push_back(seg.p1);
        if( onSegment(vs[i].p1,vs[i].p2,seg.p2) ) vp.push_back(seg.p2);
      } else if( intersectLS(seg,vs[i]) ) vp.push_back(crosspoint(vs[i],seg));
    }
    vir = vs[i].p1;
    sort(vp.begin(),vp.end(),comp);
    vp.erase(unique(vp.begin(),vp.end()),vp.end());
    rep(j,(int)vp.size()-1) ret.push_back(Segment(vp[j],vp[j+1]));
  }
  return ret;
}
 
int main(){
  rep(i,1<<16) bc[i] = __builtin_popcount(i);
  while( cin >> n, n ){
    rep(i,n) cin >> ps[i].x >> ps[i].y;
    poly.resize(n);
    rep(i,n) poly[i] = ps[i]; 
    segs = makeGraph();
    //rep(i,segs.size()) cout << segs[i] << endl;
    //cout << check (552) << endl;
    //return 0;
    int ans = n;
    rep(i,(1<<n)) {
      if( bc[i] >= ans ) continue;
      if( check(i) ) ans = bc[i];
    }
    cout << ans << endl;
  }
  return 0;
}

Measured memory_bytes: 1628