from heapq import * N=int(input()) point=[tuple(map(int,input().split())) for _ in range(N)] d=set() res=0 for i in range(1,N): que=[] heapify(que) for j in range(N): if i==j: continue xi,yi=point[i] xj,yj=point[j] dist=((xi-xj)**2+(yi-yj)**2)**0.5 heappush(que,(dist,j)) while(que[0][1] in d): heappop(que) if que[0][1]==0: d.add(i) res+=1 print(res)