using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
static class Program{
	const int mod=(int)1e9+7;
	static void Main(){
		Sc sc=new Sc();
		int n=sc.I,p;
		StringBuilder sb=new StringBuilder();
		while(n!=0){
			p=0;
			var a=new double[n][];
			for(int i=0;i<n;i++){
				a[i]=Array.ConvertAll(Console.ReadLine().Split(','),double.Parse);
				if(a[i][1]<a[p][1]){p=i;}
				else if(a[i][1]==a[p][1]&&a[i][0]<a[p][0]){p=i;}
			}
			Gs gs=new Gs(a,p,true);
			sb.Append((n-gs.li.Count)+"\n");
			n=sc.I;
		}
		Console.Write(sb);
	}
}
public class Gs{
	public class Dt{
		public int n;
		public double x,y;
		public double d;
		public Dt(double d,int n,double x,double y){this.d=d;this.n=n;this.x=x;this.y=y;}
	}
	private Dt[] arr;
	private double cd,cx;
	public List<Dt> li=new List<Dt>();
	public Gs(double[][] a,int p,bool b){
		int n=a.Length,q=2;
		arr=new Dt[n];
		for(int i=0;i<n;i++){
			if(i!=p){arr[i]=new Dt(Atan2(a[i][1]-a[p][1],a[i][0]-a[p][0])*180/PI,i,a[i][0],a[i][1]);cd=Max(cd,arr[i].d);}
		}
		arr[p]=new Dt(-512,p,a[p][0],a[p][1]);
		if(b){
			Array.Sort(arr,Ca1);
			li.Add(arr[0]);li.Add(arr[1]);
			while(q!=n){
				li.Add(arr[q]);
				q++;
				while(li.Count>2&&(li[li.Count-1].x-li[li.Count-2].x)*(li[li.Count-3].y-li[li.Count-2].y)-(li[li.Count-1].y-li[li.Count-2].y)*(li[li.Count-3].x-li[li.Count-2].x)<=0){li.RemoveAt(li.Count-2);}
			}
		}
		else{
			cx=a[p][0];
			Array.Sort(arr,Ca2);
			li.Add(arr[0]);li.Add(arr[1]);
			while(q!=n){
				li.Add(arr[q]);
				q++;
				while(li.Count>2&&(li[li.Count-1].x-li[li.Count-2].x)*(li[li.Count-3].y-li[li.Count-2].y)-(li[li.Count-1].y-li[li.Count-2].y)*(li[li.Count-3].x-li[li.Count-2].x)<0){li.RemoveAt(li.Count-2);}
			}
		}
	}
	private int Ca1(Dt a,Dt b){
		if(a.d>b.d){return 1;}
		else if(a.d<b.d){return -1;}
		else if(a.y>b.y){return 1;}
		else if(a.y<b.y){return -1;}
		else if(a.x<b.x){return 1;}
		else if(a.x>b.x){return -1;}
		return 0;
	}
	private int Ca2(Dt a,Dt b){
		if(a.d>b.d){return 1;}
		else if(a.d<b.d){return -1;}
		else if(a.d==cd){
			if(cx==a.x){if(a.y<b.y){return 1;}else if(a.y>b.y){return -1;}}
			else if(cx>a.x){if(a.x>b.x){return 1;}else if(a.x<b.x){return -1;}}
			else{if(a.x<b.x){return 1;}else if(a.x>b.x){return -1;}}
		}
		else{
			if(cx==a.x){if(a.y>b.y){return 1;}else if(a.y<b.y){return -1;}}
			else if(cx<a.x){if(a.x>b.x){return 1;}else if(a.x<b.x){return -1;}}
			else{if(a.x<b.x){return 1;}else if(a.x>b.x){return -1;}}
		}
		return 0;
	}
	public double Diameter(){//直径
		double q=(li[0].x-li[li.Count-1].x),p=(li[0].y-li[li.Count-1].y),d=Math.Sqrt(q*q+p*p);
		for(int i=1;i<li.Count;i++){
			q=(li[i].x-li[i-1].x);
			p=(li[i].y-li[i-1].y);
			d+=Sqrt(q*q+p*p);
		}
		return d;
	}
}

public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),int.Parse);}
	public int[] Ia3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),long.Parse);}
	public long[] La3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),long.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
}


Measured memory_bytes: 13876