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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;


public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.next();
        String[] str2 = new String[3];
        str2 = str.split("");
        Arrays.sort(str2);
        if( !(str2[1].equals(str2[2])) && str2[0].equals(str2[1]) && str2[2].equals(str2[3])) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    }
}