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.*;


public class Main {
	
	
	public static void main(String[] args) {

		Scanner s = new Scanner(System.in);
		char[] st = s.next().toCharArray();
		int[] a = new int[26];
		for(int i = 0;i<4;i++)
			a[st[i]-'A']++;
		
		int c=  0;
		for(int i=0;i<26;i++)
		{
			if(a[i]>0 && a[i]==2)
				c++;
		}
		if(c==2)System.out.println("Yes");
		else System.out.println("No");
	}
}