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 (2.7.1) (judge verdict: Accepted)

s = gets.chomp.split("")
long = s.size
ans = 0
arr = []
(0..long-1).each do |i|
    j = 0
    count = 0
    while true
        #p j
        #p long -1
        if s[i] == s[j]
            count += 1
        end
        if j >= 3
            arr << count
             break
        end
        j += 1
    end
end
ans = 0
    (1..3).each do |i|
      if arr[i] == arr[i-1] && arr.inject(:+) == 8
        ans += 1
      end

    
    end
    if ans >= 3
        puts "Yes"
    else
        puts "No"
    end