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 sc = new Scanner(System.in);		
		String s = sc.next();
        String t = "No";
        if(s.charAt(0)==s.charAt(1))
        {if(s.charAt(2)==s.charAt(3) && s.charAt(0)!=s.charAt(2)){t = "Yes";}}
		 if(s.charAt(0)==s.charAt(2))
        {if(s.charAt(1)==s.charAt(3) && s.charAt(0)!=s.charAt(1)){t = "Yes";}}
         if(s.charAt(0)==s.charAt(3))
        {if(s.charAt(1)==s.charAt(2) && s.charAt(0)!=s.charAt(1)){t = "Yes";}}  
            System.out.println(t);
	}
}