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: Runtime Error)

"use strict"
 
const main = lines => {
 
  const wordArr = [...lines[0]]
  
  let map = {}
  wordArr.forEach(w => {
   	map[w] = map[w] ? map[w] + 1 : 1
  })
  
  const result = Object.values(map).every(v => v === 2) ? "YES" : "NO"
  
  console.log(result)
 
}
  
main(require('fs').readFileSync('/dev/stdin', 'utf8').split('\n'))