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)

var str = [];
var count = 0;

function Main(input) {

	input = input.split("");
	
	for(var i = 0;i < 4;i++){
	    str[i] = input[i];
	}
	
	for(var j = 1;j < 4;j++){
	    if(str[0]===str[j]){
	        count++;
	        if(j===1){
	            if(str[0]===str[2]||str[0]===str[3]||str[1]===str[2]||str[1]===str[3]){
	                console.log("No");
	                return 0;
	            }else if(str[2]===str[3]){
	                console.log("Yes");
	                return 0;
	            }else{
	                console.log("No");
	                return 0;
	            }
	        }else if(j===2){
	            if(str[0]===str[1]||str[0]===str[2]||str[1]===str[0]||str[1]===str[2]){
	                console.log("No");
	                return 0;
	            }else if(str[1]===str[3]){
	                console.log("Yes");
	                return 0;
	            }else{
	                console.log("No");
	                return 0;
	            }
	        }else if(j===3){
	            if(str[0]===str[2]||str[0]===str[4]||str[3]===str[2]||str[3]===str[1]){
	                console.log("No");
	                return 0;
	            }else if(str[1]===str[2]){
	                console.log("Yes");
	                return 0;
	            }else{
	                console.log("No");
	                return 0;
	            }
	        }
	    }
	}
	if(count===0){
	    console.log("No");
	}
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));