inp = [int(l.strip()) for l in open("1.dat").readlines()]

gnums = sorted(inp)
tgt = 2020
orglen = len(gnums)

def bis(l, diff):
  half = round(len(l)/2)
  ll, ul = l[:half], l[half:]
  tl = ul if ul and ul[0] <= diff else ll
  if tl and tl[0] > diff:
    return []
  if len(tl) > 1:
    tl = bis(tl, diff)
  return tl

def solve_a_bis(nums):
  while(len(nums)):
    num = nums.pop(0)
    diff = tgt - num
    l = bis(nums, diff)
    if len(l) and num + l[0] == tgt:
      print("solve a bis", num, l[0], num*l[0])
      break

def solve_a_brute(nums):
  while(len(nums)):
    num = nums.pop(0)
    diff = tgt - num
    if diff in nums:
      print("solve a brute", num, diff, num*diff)
      break

solve_a_bis(list(gnums))

def solve_b(nums):
  rnums = list(reversed(nums))
  while len(rnums):
    num = rnums.pop(0)
    for i, nnum in enumerate(rnums):
      nsum = num + nnum
      if nsum >= tgt:
        continue
      diff = tgt - nsum
      if diff in rnums[i:]:
        print("solve b", num, nnum, diff, num * nnum * diff)
        return

solve_b(list(gnums))