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.Scanner;

public class Main {
    public static void main(String args[]) {
        try (Scanner in = new Scanner(System.in)) {
            String s = in.next();
            if (s.charAt(0) == s.charAt(1)) {
                if (s.charAt(2)!=s.charAt(0) && s.charAt(2) == s.charAt(3)) {
                    System.out.println("Yes");
                    return;
                }
            } else if (s.charAt(0) == s.charAt(2)) {
                if (s.charAt(1)!=s.charAt(0) && s.charAt(1) == s.charAt(3)) {
                    System.out.println("Yes");
                    return;
                }
            } else if (s.charAt(0) == s.charAt(3)) {
                if (s.charAt(1)!=s.charAt(0) && s.charAt(1) == s.charAt(2)) {
                    System.out.println("Yes");
                    return;
                }
            }
            System.out.println("No");
        }
    }
}