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: Wrong Answer)

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		char[] input= sc.next().toCharArray();
		Map<Character,Integer> map  = new HashMap<Character,Integer>();
		for(int i=0;i<input.length;i++) {
			if(!map.containsKey(input[i])) {
				map.put(input[i],0);
			}else {
				map.put(input[i],map.get(input[i])+1);
				if(map.get(input[i])>=2)System.out.println("No");
			}
		}
		if(map.size()!=2) System.out.println("No");
		else System.out.println("Yes");
	}
}