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 Ruby (2.3.3) (judge verdict: Wrong Answer)

s = gets.chomp
#puts "#{s}"
moji = s.chars
#puts "#{moji}"
moji.sort!
#puts "#{moji}"

if (moji[0] == moji[1] || moji[2] == moji[3])
    if moji[0] == moji[2]
        puts "No"
    else 
        puts "Yes"
    end
else
    puts "No"
end