import sys
from math import hypot

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for k in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10**9)
INF = 10**19
MOD = 10**9 + 7
EPS = 10**-10

N = INT()
XY = [()] * N
for i in range(N):
    x, y = MAP()
    XY[i] = (x, y)

nodes = [[] for i in range(N)]
for i, (x, y) in enumerate(XY):
    for j, (x2, y2) in enumerate(XY[i+1:], i+1):
        dist = hypot(x-x2, y-y2) / 2
        nodes[i].append((dist, j))
        nodes[j].append((dist, i))

for i in range(N):
    nodes[i].sort()

ans = 0
removed = [0] * N
for _, i in nodes[0]:
    if not removed[i]:
        for _, j in nodes[i]:
            if j == 0:
                removed[i] = 1
                ans += 1
                break
            if not removed[j]:
                removed[i] = 1
                removed[j] = 1
                break
print(ans)