from collections import deque import sys def dist(P,Q): a,b=P[0]-Q[0],P[1]-Q[1] return a*a+b*b def main(): N=int(input()) P=[0]*N for i in range(N): P[i]=tuple(map(int,input().split())) Q=[0]*(N*(N-1)//2) k=0 for i in range(N): for j in range(i+1,N): Q[k]=(dist(P[i],P[j]),j,i) k+=1 Q.sort() Q=deque(Q) Flag=[True for _ in range(N)] X=0 while Q: (_,j,i)=Q.popleft() if not(Flag[i] and Flag[j]): continue Flag[j]=False if i!=0: Flag[i]=False else: X+=1 print(X) main()