from math import sqrt
import sys

input = sys.stdin.readline

def main():
    n = int(input())
    P = [list(map(int, input().split())) for _ in range(n)]

    L = []
    for i in range(n):
        for j in range(i + 1, n):
            L.append(((P[i][0] - P[j][0])**2 + (P[i][1] - P[j][1])**2, i, j))

    L.sort(key=lambda x: x[0])
    seen = set()
    ans = 0
    for _, i, j in L:
        if i == 0:
            if j in seen:
                continue
            ans += 1
            seen.add(j)
        else:
            if i in seen or j in seen:
                continue
            seen.add(i)
            seen.add(j)
    print(ans)

if __name__ == '__main__':
    main()