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 Java7 (OpenJDK 1.7.0) (judge verdict: Runtime Error)

package sd;

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

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