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 (2.13.1) (judge verdict: Accepted)

import io.StdIn.readLine 

object Main {
  def main(args: Array[String]): Unit = {
    var s = readLine().sorted
    if(s(0) == s(1) && s(2) == s(3) && s(0) != s(2)){
      println("Yes")
    }else{
      println("No")
    }
  }
}