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 Kotlin (1.0.0) (judge verdict: Wrong Answer)

fun main(args:Array<String>){
    val str = readLine()!!
    var flag = false
    if(str[0]==str[1]){
        if(str[2]==str[3])flag=true
    }else if(str[0]==str[2]){
        if(str[1]==str[3])flag=true
    }else if(str[0]==str[3]){
        if(str[1]==str[2])flag=true
    }else if(str[1] ==str[2]){
        if(str[0]==str[3])flag=true
    }else if(str[1]==str[3]){
        if(str[2]==str[0])flag=true
    }else if(str[2]==str[3]){
        if(str[0]==str[1])flag=true
    }
    if(flag){
        println("Yes")
    }else{
        println("No")
    }
}