#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define RD(v) int v=0;{int c;while(c=*r++-48,c>=0)v=v*10+c;}
#define RDS(v) int v=0;{int c,s;s=*r=='-'?++r,1:0;while(c=*r++-48,c>=0)v=v*10+c;v=s?-v:v;}

int x[1000],y[1000],c[1000];
int al[1000],af[1001],an;

main(){
	char*r=mmap(0l,24l*1024,1,2,0,0l);

	RD(n);
	for(int i=0;i<n;++i){
		RDS(a); x[i]=a;
		RDS(b); y[i]=b;
	}
	for(int i=0;i<n;++i){
		c[i]=n;
		af[i]=1;
		al[i]=i;
	}

	int z=0;
	for(an=n;an!=1;){
		for(int ai=1;ai<an;++ai){
			int i=al[ai];
			if(!af[c[i]]){
				long dmin=1l<<62;
				for(int aj=0;aj<an;++aj){
					int j=al[aj];
					if(j!=i){
						int dx=x[j]-x[i];
						int dy=y[j]-y[i];
						long d=(long)dx*dx+(long)dy*dy;
						if(dmin>d){
							dmin=d;
							c[i]=j;
						}
					}
				}
			}
		}
		int an1=1;
		for(int ai=1;ai<an;++ai){
			int i=al[ai];
			if(c[i]==0){
				af[i]=0;
				++z;
			}else if(c[c[i]]==i){
				af[i]=0;
			}else{
				al[an1++]=i;
			}
		}
		an=an1;
	}
	printf("%d",z);
}