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: Accepted)

import java.util.*;

public class Main {

    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        String S = scan.next();

        char[] array = S.toCharArray();

        if(array[0] == array[1] && array[2] == array[3] && array[1] != array[2]){

            System.out.println("Yes");
            return;

        }else if(array[0] == array[2] && array[1] == array[3] && array[1] != array[2]){

            System.out.println("Yes");
            return;

        }else if (array[0] == array[3] && array[1] == array[2] && array[0] != array[1]){

            System.out.println("Yes");
            return;
        }
        
        System.out.println("No");
        return;

    }
}