main = do
  contents <- readFile "day1.txt"
  let xs = map read $ lines contents
  let [(i, j, k)] = [(i, j, k) | i <- [0..(length xs)-1],
                                 j <- [0..i],
                                 k <- [0..j],
                                 (xs !! i) + (xs !! j) + (xs !! k) == 2020]
  print $ (xs !! i) * (xs !! j) * (xs !! k)