import Control.Monad

import Data.Array

yoba rangeArr end start = minimumOp [arr ! (end, x) | x <- [0 .. sizeX]]
 
  where bounds' @ ((0, 0), (sizeY, sizeX)) = bounds rangeArr
        
        arr = listArray bounds' [value y x | y <- [0 .. sizeY], x <- [0 .. sizeX]]
        
        value y _ | y == start = Just 0
        value _ 0              = Nothing
        value y x              = minimumOp [(arr ! (n, x - 1)) `addOp` (rangeArr ! (n, y)) | n <- [0 .. sizeY]]
                                        
        addOp = liftM2 (+)
        
        minimumOp = foldl minOp Nothing
        
          where Just v1 `minOp` Just v2 = Just $ min v1 v2
                Just v1 `minOp` Nothing = Just v1
                Nothing `minOp` Just v2 = Just v2
                Nothing `minOp` Nothing = Nothing        
         

main = print $ yoba (toArray2D graph) end start

  where end   = 4
        start = 0
                    
        graph = [[Nothing, Just  7, Just  9, Nothing, Nothing, Just 14],
                 [Just  7, Nothing, Just 10, Just 15, Nothing, Nothing],
                 [Just  9, Just 10, Nothing, Just 11, Nothing, Just  2],
                 [Nothing, Just 15, Just 11, Nothing, Just  6, Nothing],
                 [Nothing, Nothing, Nothing, Just  6, Nothing, Just  9],
                 [Just 14, Nothing, Just  2, Nothing, Just  9, Nothing]]
                 
        toArray2D source = listArray ((0, 0), (size, size)) [source !! y !! x | y <- [0 .. size], x <- [0 .. size]]
                   
          where size = length source - 1