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 Scala (2.11.7) (judge verdict: Accepted)

import java.util.Scanner

object Main {
  def isNum(ch: Char): Boolean = {
    val ret = ch match {
      case '0' => true
      case '1' => true
      case '2' => true
      case '3' => true
      case '4' => true
      case '5' => true
      case '6' => true
      case '7' => true
      case '8' => true
      case '9' => true
      case _ => false
    }
    return ret
  }
  def main(args: Array[String]): Unit = {
    val sc = new Scanner(System.in)
    val a, b = sc.nextInt()
    val s = sc.next()
//    println(s)
    var f = true
    for(i <- 0 until a) {
      f = isNum(s(i))
//      println(i)
    }
    if(f) {
//      println("Yes")
    } else {
      println("No")
      return
    }
    f = if(s(a)!='-') {
      false
    } else {
      true
    }
    if(f) {
//      println("Yes")
    } else {
      println("No")
      return
    }
//    println(a + " " + b)
    for(i <- a+1 until a+b+1) {
      f = isNum(s(i))
//      println(i)
    }
    if(f) {
      println("Yes")
    } else {
      println("No")
    }
  }
}