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 str = sc.next();

        char c0 = str.charAt(0);
        char c1 = str.charAt(1);
        char c2 = str.charAt(2);
        char c3 = str.charAt(3);

        if ((c0 == c1 && c2 == c3 & c0 != c2)
            || (c0 == c2 && c1 == c3 & c0 != c1)
                || (c0 == c3 && c1 == c2 & c0 != c1)) {

            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    }
}