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)

# input = readlines()
# n, a, b = input.shift().chomp.split("\s").map{|x| x.to_i}

s = gets().chomp

h = {}

s.split('').each do |char|
  h[char] = 0 if h[char].nil?
  h[char] += 1
end

res = true
h.values.each do |cnt|
  res = false if cnt != 2
end

puts res == true ? 'Yes' : 'No'