Problem:
Score : 100 points

Problem Statement

You are given a 4-character string S consisting of uppercase English letters.
Determine if S consists of exactly two kinds of characters which both appear twice in S.

Constraints

The length of S is 4.

S consists of uppercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If S consists of exactly two kinds of characters which both appear twice in S, print Yes; otherwise, print No.

Sample Input 1

ASSA

Sample Output 1

Yes

S consists of A and S which both appear twice in S.

Sample Input 2

STOP

Sample Output 2

No

Sample Input 3

FFEE

Sample Output 3

Yes

Sample Input 4

FREE

Sample Output 4

No

Solution in Scala (2.11.7) (judge verdict: Wrong Answer)

object Main extends App {

  val s: Array[String] = scala.io.StdIn.readLine().split("")


  def solve(): String = {
    println(s.mkString(","))
    s.foreach { c =>
      if(s.count(_ == c) != 2) return "No"
    }
    "Yes"
  }

  println(solve)

}