content: --- >>> matrix
  -- <command line>: unknown package: main
  
  matrix :: [Int]
  matrix =  [08, 02, 22, 97, 38, 15, 00, 40, 00, 75, 04, 05, 07, 78, 52, 12, 50, 77, 91, 08,
              49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 04, 56, 62, 00,
              81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 03, 49, 13, 36, 65,
              52, 70, 95, 23, 04, 60, 11, 42, 69, 24, 68, 56, 01, 32, 56, 71, 37, 02, 36, 91,
              22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80,
              24, 47, 32, 60, 99, 03, 45, 02, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50,
              32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70,
              67, 26, 20, 68, 02, 62, 12, 20, 95, 63, 94, 39, 63, 08, 40, 91, 66, 49, 94, 21,
              24, 55, 58, 05, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72,
              21, 36, 23, 09, 75, 00, 76, 44, 20, 45, 35, 14, 00, 61, 33, 97, 34, 31, 33, 95,
              78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 03, 80, 04, 62, 16, 14, 09, 53, 56, 92,
              16, 39, 05, 42, 96, 35, 31, 47, 55, 58, 88, 24, 00, 17, 54, 24, 36, 29, 85, 57,
              86, 56, 00, 48, 35, 71, 89, 07, 05, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58,
              19, 80, 81, 68, 05, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 04, 89, 55, 40,
              04, 52, 08, 83, 97, 35, 99, 16, 07, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66,
              88, 36, 68, 87, 57, 62, 20, 72, 03, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69,
              04, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 08, 46, 29, 32, 40, 62, 76, 36,
              20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 04, 36, 16,
              20, 73, 35, 29, 78, 31, 90, 01, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 05, 54,
              01, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 01, 89, 19, 67, 48]
  
  withOffset :: Int -> Int -> [Int]
  withOffset y x = [x, x + y, x + y*2, x + y*3]
  
  horizontal :: Int -> [Int]
  horizontal = withOffset 1
  
  vertical :: Int -> [Int]
  vertical = withOffset 20
  
  diagonal :: Int -> [Int]
  diagonal = withOffset 19
  
  diagonal2 :: Int -> [Int]
  diagonal2 = withOffset 21
  
  indexBy :: Int -> Int -> Int
  indexBy row column = row*20 + column
  
  indicesBy :: [Int] -> [Int] -> [Int]
  indicesBy rows columns= [indexBy row column | row <- rows, column <- columns]
  
  horizontalIndices :: [Int]
  horizontalIndices = indicesBy [0..19] [0..16]
  
  verticalIndices :: [Int]
  verticalIndices = indicesBy [0..16] [0..19]
  
  diagonalIndices :: [Int]
  diagonalIndices = indicesBy [0..16] [3..19]
  
  diagonal2Indices :: [Int]
  diagonal2Indices = indicesBy [0..16] [0..16]
  
  horizontalGroups :: [[Int]]
  horizontalGroups = map horizontal horizontalIndices
  
  verticalGroups :: [[Int]]
  verticalGroups = map vertical verticalIndices
  
  diagonalGroups :: [[Int]]
  diagonalGroups = map diagonal diagonalIndices
  
  diagonal2Groups :: [[Int]]
  diagonal2Groups = map diagonal2 diagonal2Indices
  
  multiplyByMatrixValueByIndex :: [Int] -> Int
  multiplyByMatrixValueByIndex x = product (map (matrix !!) x)
  
  maxHorizontal :: Int
  maxHorizontal = maximum (map multiplyByMatrixValueByIndex horizontalGroups)
  
  maxVertical :: Int
  maxVertical = maximum (map multiplyByMatrixValueByIndex verticalGroups)
  
  maxDiagonal :: Int
  maxDiagonal = maximum (map multiplyByMatrixValueByIndex diagonalGroups)
  
  maxDiagonal2 :: Int
  maxDiagonal2 = maximum (map multiplyByMatrixValueByIndex diagonal2Groups)
  
  maxFinal :: Int
  maxFinal = maximum [maxHorizontal, maxVertical, maxDiagonal, maxDiagonal2]
  
  main :: IO ()
  main = print maxFinal
  