from operator import itemgetter
n=int(input())
baloons=[tuple(map(int,input().split())) for i in range(n)]
d=[]
cnt=0
for i in range(n-1):
    for j in range(i+1,n):
        d.append([(baloons[i][0]-baloons[j][0])**2+(baloons[i][1]-baloons[j][1])**2,i,j])
d.sort(key=itemgetter(0))
used=[0 for i in range(n)]
for i in range(int(n*(n-1)/2)):
    if(used[d[i][1]]==0 and used[d[i][2]]==0):
        if(d[i][1]==0):
            cnt+=1
            used[d[i][2]]=1
        else:
            used[d[i][1]]=1
            used[d[i][2]]=1
print(cnt)