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 inputArr = input.split("");
    var ret = {};
    for (str of  inputArr) {
		ret[str] = ret[str] ? ret[str] + 1 : 1;
    }
    if (Object.keys(ret).length === 2 && ret[Object.keys(ret)[0]] === 2) {
        console.log('Yes');
    } else {
        console.log('No');
    }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));