#include <iostream>
#include <vector>
#include <complex>
#include <algorithm>
using namespace std;
static const double EPS = 1e-10;
typedef long long ll;
#define REP(i, s, e) for ( int i = s; i <= e; i++ )  
 
const double INF = 1e12;
typedef complex<double> P,point;
typedef vector<P> G,polygon;
namespace std {bool operator < (const P& a, const P& b) {return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);} }
double cross(const P& a, const P& b) {return imag(conj(a)*b);}
double dot(const P& a, const P& b) {return real(conj(a)*b);}
struct L : public vector<P> {L(const P &a, const P &b) {push_back(a); push_back(b);} };
inline int ccw(P a, P b, P c) {
	b -= a; c -= a;
	if (cross(b, c) > 0)   return +1;
	if (cross(b, c) < 0)   return -1;
	if (dot(b, c) < 0) return +2;
	if (norm(b) < norm(c)) return -2;
	return 0;
}

 
// Check Funcs //
inline bool intersectLL(const L &l, const L &m) {return abs(cross(l[1]-l[0], m[1]-m[0])) > EPS || abs(cross(l[1]-l[0], m[0]-l[0])) < EPS;}
inline bool intersectLS(const L &l, const L &s) {return cross(l[1]-l[0], s[0]-l[0])*cross(l[1]-l[0], s[1]-l[0]) < EPS;}
inline bool intersectLP(const L &l, const P &p) {return abs(cross(l[1]-p, l[0]-p)) < EPS;}
inline bool intersectSS(const L &s, const L &t) {return ccw(s[0],s[1],t[0])*ccw(s[0],s[1],t[1]) <= 0 && ccw(t[0],t[1],s[0])*ccw(t[0],t[1],s[1]) <= 0;}
inline bool intersectSP(const L &s, const P &p) {return abs(s[0]-p)+abs(s[1]-p)-abs(s[1]-s[0]) < EPS;}

// Where is Point in Polygon? //
#define curr(P, i) P[i]
#define next(P, i) P[(i+1)%P.size()]
enum { OUT, ON, IN };
int contains(const polygon& P, const point& p) {
	bool in = false;
	for (int i = 0; i < P.size(); ++i) {
		point a = curr(P,i) - p, b = next(P,i) - p;
		if (imag(a) > imag(b)) swap(a, b);
		if (imag(a) <= 0 && 0 < imag(b))
			if (cross(a, b) < 0) in = !in;
		if (cross(a, b) == 0 && dot(a, b) <= 0) return ON;
	}
	return in ? IN : OUT;
}
P crosspoint(const L &l, const L &m) {
	double A = cross(l[1] - l[0], m[1] - m[0]);
	double B = cross(l[1] - l[0], l[1] - m[0]);
	if (abs(A) < EPS && abs(B) < EPS) return m[0];
	return m[0] + B / A * (m[1] - m[0]);
}

pair<int,int> v[65536];
int main(){
	for(int i = 0 ; i < (1<<16) ; i++){
		v[i] = make_pair(__builtin_popcount(i),i);
	}
	sort(v,v+65536);
	int N;
	while(cin >> N && N){
		vector<P> po(N);
		vector<P> chk;
		for(int i = 0 ; i < N ; i++){
			cin >> po[i].real() >> po[i].imag();
			chk.push_back(po[i]);
		}
		for(int i = 0 ; i < N ; i++){
			for(int j = i+1 ; j < N ; j++){
				for(int k = 0 ; k < N ; k++){
					L a = L(curr(po,k),next(po,k));
					L b = L(po[i],po[j]);
					if( intersectLS(b,a) ){
						chk.push_back(crosspoint(a,b));
					}
				}
			}
		}
		sort(chk.begin(),chk.end());
		vector<P> np;
		np.push_back(chk[0]);
		for(int i = 1 ; i < chk.size() ; i++){
			if( abs(chk[i]-chk[i-1]) > EPS ) np.push_back(chk[i]);
		}
		chk = np;
		
		
		vector<int> canreach(chk.size());
		for(int i = 0 ; i < chk.size() ; i++){
			//cout << chk[i] << " ";
			for(int j = 0 ; j < N ; j++){
				L l = L(chk[i],po[j]);
				
				//とりあえず中点が外部にあったら外側を走っていることは確定するのでcontinue;
				if( contains(po,0.5*(chk[i]+po[j])) == OUT ) continue; 
				
				int ok = 1;
				for(int k = 0 ; k < N ; k++){
					L a = L(curr(po,k),next(po,k));
					if( intersectSP(a,chk[i])|| intersectSP(a,po[j]) ) continue;
					if( intersectSS(a,l) ){
						P cp = crosspoint(a,l);
						
						if( abs(cp-curr(po,k)) > EPS && abs(cp-next(po,k)) > EPS ){
							ok = 0;
							break;
						}
					}
				}
				canreach[i] |= (ok<<j);
			}
			//chk[i]は辺上の点なので、少なくともある頂点(a,b)を結ぶ辺上にあるならばaとbにはたどり着ける。
			for(int k = 0 ; k < N ; k++){
				L a = L(curr(po,k),next(po,k));
				if( intersectSP(a,chk[i]) ){
					canreach[i] |= 1<<(k);
					canreach[i] |= 1<<((k+1)%N);
				}
			}
		}
		for(int I = 0 ; I < (1<<16) ; I++){
			int i = v[I].second;
			int flag = 1;
			for(int j = 0 ; j < chk.size() ; j++){
				if( !(canreach[j]&i) ){
					flag = 0;
					break;
				}
			}
			if( flag ){
				cout << v[I].first << endl;
				break;
			}
		}
				
	}
}

Measured memory_bytes: 1828