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)

function Main(input) {
	var str0 = input.charAt(0);
  	var str1 = input.charAt(1);
  	var str2 = input.charAt(2);
  	var str3 = input.charAt(3);
  	if (str0 == str1 && str0 == str2 && str0 == str3){
      console.log("No");
    } else if (str0 == str1 && str2 == str3) {
          console.log("Yes");
    } else if (str0 == str2 && str1 == str3){
          console.log("Yes");
   	} else if (str0 == str3 && str1 == str2){
	  console.log("Yes");
    } else {
      console.log("No");
    }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));