n = read_line.to_i
ps = Array.new(n) { read_line.split.map(&.to_i) }
cs = Array.new(90) { [] of Int32 }
ps.each.with_index do |p, i|
  x, y = p
  yi = y % 9
  x += y // 9 % 2 * 5
  xi = x % 10
  idx = yi * 10 + xi
  cs[idx] << i + 1
end
cs.each do |c|
  if c.size * 90 >= n
    puts c.size
    puts c.join(" ")
    break
  end
end