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 Perl (v5.18.2) (judge verdict: Wrong Answer)

$s=<>;
@ary=split//,$s;
@ary = sort {$a cmp $b} @ary;
if($ary[0] eq $ary[1] && $ary[2] eq $ary[3]){
	if($ary[0] ne $ary[2] && $ary[1] ne $ary[3] ){
    	print "Yes";
    } else {
    	print "No";
    }
}else{
	print"No";
}