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 OCaml (4.02.3) (judge verdict: Accepted)

let calc_ a b s =
    match BatString.split_on_char '-' s with
    | [x; y] -> String.length x = a && String.length y = b
    | _ -> false

let calc a b s =
    let f v i c = v && (if i = a then c = '-' else c <> '-') in
    BatString.fold_lefti f true s

let main =
    let [a; b] = read_line () |> BatString.split_on_char ' ' |> List.map int_of_string in
    let s = read_line () in
    let v = (calc a b s) in
    print_endline (if v then "Yes" else "No")