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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

"use strict";
    
const main = arg => {
  	let txtArr = arg.split("");
  	let ans = 'No';
	let NewArr = txtArr.sort();
  	if((NewArr[0] == NewArr[1]) && (NewArr[2] == NewArr[3]) && (NewArr[1] != NewArr[3])){
    	ans = 'Yes';
    }
  	console.log(ans);
  	
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));