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)

// inputに入力データ全体が入る
function Main(input) {
    var S = input;
    var targetStr = S[0]
    var targetStr2 = S[2]
    var count = (S.match(new RegExp(targetStr, "g" ))||[]).length;
    var count2 = (S.match(new RegExp(targetStr2, "g" ))||[]).length;
    if(count == 2 && count2 == 2){
        console.log("Yes")
    }else{
        console.log("No")
    }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));