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)

function Main(input) {
  var inputList = [];
  for(var i = 0; i < input.length; i++){
    inputList.push(input.slice(i, i + 1));
  }
  if((inputList[0] == inputList[1] && inputList[0] != inputList[2] && inputList[0] != inputList[3])
    || (inputList[0] != inputList[1] && inputList[0] == inputList[2] && inputList[0] != inputList[3])
    || (inputList[0] != inputList[1] && inputList[0] != inputList[2] && inputList[0] == inputList[3])){
     console.log("Yes");
     }else{
       console.log("No");
     }
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));