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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;
 
class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    
    String S = sc.next();
    if(S.charAt(0) == S.charAt(1) && S.charAt(2) == S.charAt(3) && S.charAt(0) != S.charAt(2)){
      System.out.println("YES");
    } else if(S.charAt(0) == S.charAt(2) && S.charAt(1) == S.charAt(3) && S.charAt(0) != S.charAt(1)){
      System.out.println("YES");
    } else if(S.charAt(0) == S.charAt(3) && S.charAt(1) == S.charAt(2) && S.charAt(0) != S.charAt(1)){
      System.out.println("YES");
    } else {
      System.out.println("NO");
    }
  }
}