Submission #162938

---

Source Code Expand

{-# LANGUAGE CPP #-}
#ifndef HDEVTOOLS
{-# OPTIONS_GHC -O2 -funbox-strict-fields #-}
#endif
{-# LANGUAGE BangPatterns, ViewPatterns, OverloadedStrings #-}

import Control.Applicative
import Control.Monad
import Data.Maybe
import Data.List
import qualified Data.ByteString.Char8 as S
import qualified Data.Vector.Unboxed as U
import Numeric
import Data.Char

main :: IO ()
main = do
  [a, succ -> b] <- map read . words <$> getLine
  print $ solve a b

solve :: Int -> Int -> Int
solve lo hi = (hi - lo) - (legalIndex hi - legalIndex lo)

legalIndex :: Int -> Int
legalIndex n = case readOct (map tr $ floorAvailable $ show (n-1)) of
  [(r, "")] -> fromIntegral r + 1
  _ -> error "parse error"
  where
    tr = ("0123X45678X"!!) . digitToInt

floorAvailable :: String -> String
floorAvailable [] = []
floorAvailable ('4':cs) = '3' : map (const '8') cs
floorAvailable ('9':cs) = '8' : map (const '8') cs
floorAvailable (c:cs) = c : floorAvailable cs

readInt :: S.ByteString -> Int
readInt s = case S.readInt s of
  Just (r, "") -> r
  _ -> error $ "not an integer: " ++ show s

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