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 scanner = new Scanner(System.in);

    char[] array = scanner.next().toCharArray();

    int count = 0;

    for(int i = 0; i < array.length; i++) {
      for(int l = 0; l < array.length; l++) {
        if(i == l) {
          continue;
        }
        count += array[i] == array[l] ? 1 : 0;
      }
    }

    System.out.println(count == 4 ? "Yes" : "No");

    scanner.close();
  }
}