Problem:
Score : 200 points

Problem Statement

The postal code in Atcoder Kingdom is A+B+1 characters long, its (A+1)-th character is a hyphen -, and the other characters are digits from 0 through 9.

You are given a string S. Determine whether it follows the postal code format in Atcoder Kingdom.

Constraints

1≤A,B≤5

|S|=A+B+1

S consists of - and digits from 0 through 9.

Input

Input is given from Standard Input in the following format:

A B
S

Output

Print Yes if S follows the postal code format in AtCoder Kingdom; print No otherwise.

Sample Input 1

3 4
269-6650

Sample Output 1

Yes

The (A+1)-th character of S is -, and the other characters are digits from 0 through 9, so it follows the format.

Sample Input 2

1 1
---

Sample Output 2

No

S contains unnecessary -s other than the (A+1)-th character, so it does not follow the format.

Sample Input 3

1 2
7444

Sample Output 3

No

Solution in Haskell (GHC 7.10.3) (judge verdict: Wrong Answer)

import Data.List.Split
import Data.Char

main :: IO ()
main = do
  [a,b] <- map read . words <$> getLine
  s <- getLine
  putStrLn $ if f s a b then "Yes" else "No"

f :: String -> Int -> Int -> Bool
f s a b
  | (head $ drop a s) /= '-' = False
  | length s == a+b+1 = True
  | otherwise  =
      all (&&True) $ concatMap (map isDigit . show) (splitOn "-" s)