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 12.16.1) (judge verdict: Accepted)

function main(input) {
   input = input.trim();
  const a = input.split("");
  a.sort();
  console.log(a[0] == a[1]
		    &&a[2] == a[3]
		    &&!(a[0] == a[2])?"Yes":"No");
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));