N = int(input())
lsxy = [tuple(map(int,input().split())) for i in range(N)]
ls = []
for i in range(N-1):
    for j in range(i+1,N):
        dist = (lsxy[i][0]-lsxy[j][0])**2 + (lsxy[i][1]-lsxy[j][1])**2
        ls.append((dist,i,j))
ls.sort()
setrm = []
used = [False]*N
for i in range(len(ls)):
    d,a,b = ls[i]
    if a == 0 and used[b] == False:
        used[b] = True
        setrm.append(b)
    elif used[a] or used[b]:
        continue
    else:
        used[a] = True
        used[b] = True
print(len(setrm))