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 arg[]) {

		Scanner sc = new Scanner(System.in);

		String S = sc.next();

		char ch[] = new char[S.length()];

		int count = 0;

		for (int i = 0; i < S.length(); i++) {
			ch[i] = S.charAt(i);
		}

		for (int i = 0; i < S.length(); i++) {
			for (int j = i + 1; j < S.length(); j++) {
				if (ch[i] == ch[j]) {
					count++;
				}
			}
		}
		System.out.print(count == 2 ? "Yes" : "No");
	}
}