import sys def I(): return int(sys.stdin.readline().rstrip()) def MI(): return map(int,sys.stdin.readline().rstrip().split()) n = I() x = [] y = [] d = [] a,b = MI() x.append(a) y.append(b) for i in range(1, n): a,b = MI() x.append(a) y.append(b) for j in range(i): tmp = (x[i]-x[j])**2 + (y[i]-y[j])**2 d.append((tmp, i, j)) d.sort() deleted = [1]*n ans = 0 for i in d: if i[2] == 0: if deleted[i[1]] == 1: deleted[i[1]] = 0 ans += 1 else: if deleted[i[1]] == 1 and deleted[i[2]] == 1: deleted[i[1]] = 0 deleted[i[2]] = 0 print(ans)