N = int(input())
A = [list(map(int,input().split())) for _ in range(N)]
def d2(z,w):
    return (z[0]-w[0])**2+(z[1]-w[1])**2
B = []
for i in range(N-1):
    for j in range(i+1,N):
        B.append([d2(A[i],A[j]),i,j])
B = sorted(B,key=lambda x:x[0])
C = set()
ans = 0
for d,i,j in B:
    if i not in C and j not in C:
        if i!=0 and j!=0:
            C.add(i)
            C.add(j)
        elif i==0:
            C.add(j)
            ans += 1
        elif j==0:
            C.add(i)
            ans += 1
print(ans)