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: Accepted)

function main(input){
  const arr=input.trim().split("");

  const hunya=arr.filter(function(a){
    return a !==arr[0];
  })
  const hunyahunya=hunya.filter(function(a){
    return a !== hunya[0];
  })
  if(hunyahunya.length==0 && hunya.length==2){
    console.log("Yes");
  }else{
    console.log("No");
  }

}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));