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) {
        Scanner sc = new Scanner(System.in);

        String s = sc.next();
        String[] str = new String[4];
        str = s.split("");
        if (str[0].equals(str[1]) && str[2].equals(str[3]) && !str[1].equals(str[2]))
            System.out.println("Yes");
        else if (str[0].equals(str[2]) && str[1].equals(str[3]) && !str[1].equals(str[2]))
            System.out.println("Yes");
        else if (str[0].equals(str[3]) && str[1].equals(str[2]) && !str[1].equals(str[0]))
            System.out.println("Yes");
        else
            System.out.println("No");
    }
}