import sys input = sys.stdin.readline N = int(input()) xy = [tuple(map(int, input().split())) for _ in range(N)] l = [] for i in range(N): xi, yi = xy[i] for j in range(i+1, N): xj, yj = xy[j] l.append(((xi-xj)**2+(yi-yj)**2, i, j)) l.sort() flag = [False]*N ans = 0 for _, i, j in l: if flag[i] or flag[j]: continue if i==0: ans += 1 flag[j] = True elif j==0: ans += 1 flag[i] = True else: flag[i] = True flag[j] = True print(ans)