import numpy as np

N=int(input())
S=np.full((N,2),0)

for i in range(N):
    A,B=map(int,input().split())
    S[i][0]=A
    S[i][1]=B
    
    
count=0

while N!=1:
    
    all_diffs = np.expand_dims(S, axis=1) - np.expand_dims(S, axis=0)
    degree_distance = np.sqrt(np.sum(all_diffs ** 2, axis=-1))
    
   
    
    tmp=np.where(degree_distance==degree_distance[degree_distance>0].min())
    tmp1=tmp[0][0]
    tmp2=tmp[0][1]
    if tmp1==0:
        N-=1
        S=np.delete(S,tmp2,0)
        count+=1
    elif tmp2==0:
        N-=1
        S=np.delete(S,tmp1,0)
        count+=1
    else:
        N-=2
        #print("mohu2")
        S=np.delete(S,max(tmp1,tmp2),0)
        S=np.delete(S,min(tmp1,tmp2),0)
    #print(S)
    #print("mohu")

    
     #print("mohu")
    
print(count)