n = int(input())
ls = [list(map(int, input().split())) for _ in range(n)]
md = [0] * n
for i in range(n):
  xi, yi = ls[i]
  d = 1 << 30
  for j in range(n):
    if i == j:
      continue
    xj, yj = ls[j]
    d = min(d, (xi-xj)**2+(yi-yj)**2)
  md[i] = d
order = [i for i in range(n)]
order.sort(key = lambda x: [md[x], ls[x][0]])
ans = []
flg = [0] * n
print(n//2)
for i in order:
  if flg[i]:
    continue
  flg[i] = 1
  cnd = -1
  d = 1 << 30
  xi, yi = ls[i]
  for j in range(n):
    if flg[j]:
      continue
    xj, yj = ls[j]
    if d > (xi - xj) ** 2 + (yi - yj) ** 2:
      d = (xi - xj) ** 2 + (yi - yj) ** 2
      cnd = j
  if cnd != -1:
    print(i + 1, cnd + 1)
    flg[cnd] = 1