{-# LANGUAGE ScopedTypeVariables #-}

main = do
    lines <- readFile "2.in"
    putStrLn . show . solve . parseInput . words $ lines
    where
        solve = partB
        parseInput :: [ String ] -> [ (String, Integer) ]
        parseInput [] = []
        parseInput [x] = []
        parseInput (x:y:r) = (x, read y) : parseInput r

-- solves all lines, returns a string
partA :: [(String, Integer)] -> Integer
partA = (uncurry (*)) . foldl parseCommand (0,0)
    where
        -- (horizontal, vertical)
        parseCommand (a, b) ("forward", x) = (a + x, b)
        parseCommand (a, b) ("down", x) = (a, b + x)
        parseCommand (a, b) ("up", x) = (a, b - x)
        parseCommand _ _ = (0, 0)

partB :: [(String, Integer)] -> Integer
partB = (\(x,y,_) -> x * y) . foldl parseCommand (0, 0, 0)
    where
        -- (horiz, vert, aim)
        parseCommand (a, b, c) ("forward", x) = (a + x, b + c * x, c)
        parseCommand (a, b, c) ("down", x) = (a, b, c + x)
        parseCommand (a, b, c) ("up", x) = (a, b, c - x)
        parseCommand _ _ = (0, 0, 0)