#include<bits/stdc++.h>
using namespace std;
#define ri int
typedef long long ll;
const int maxn=2e5+10;
template<class T>inline bool ckmin(T &x,const T &y){return x>y?x=y,1:0;}
template<class T>inline bool ckmax(T &x,const T &y){return x<y?x=y,1:0;}
template<class T>inline void clear(T *arr,int siz,int val=0){memset(arr,val,sizeof(T)*(siz+1));}
int n;
int main(){
	while(~scanf("%d",&n)){
		int ans=0;
		typedef pair<int,int> pii;
		#define fi first
		#define se second
		vector<vector<pii>>v;
		for(ri i=1;i<=n;++i){
			pii p;
			scanf("%d%d",&p.fi,&p.se);
			for(auto &j:v){
				auto intersect=[&](pii x,pii y,pii z){
					return abs(1ll*(y.se-x.se)*(z.fi-y.fi))==abs(1ll*(z.se-y.se)*(y.fi-x.fi));
				};
				if(j.size()==1){j.push_back(p);goto skip;}
				else if(intersect(j[j.size()-2],j[j.size()-1],p)){j.push_back(p);goto skip;}
				else{ans+=3,j.pop_back(),j.pop_back();goto skip;}
			}
			v.push_back({p});
			skip:;
		}
		printf("%d\n",n-ans);
	}
	return 0;
}