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)

function Main(input) {
var str = input;
var no1 = str.substr(0,1);
var no2 = str.substr(1,1);
var no3 = str.substr(2,1);
var no4 = str.substr(3,1);

const isUpperCase = c => {
  return /^[A-Z]+$/g.test(c)
}
 if(isUpperCase(str)==false){
   console.log(No);
   break;
 }
  if (no1===no2&&no3===no4) {
    console.log('Yes');
  }else if (no1===no4&&no3===no2) {
    console.log('Yes');
  }else {
    console.log('No');
  }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));