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: Accepted)


def solve()
  input1 = readline()
  array = []
  cnt = 0

  for num in 0..3 do
    array.push(input1[num])
  end

  for i in 0..3 do
    if array.count(input1[i]) == 2 then
      cnt += 1
    end
  end

  if cnt == 4 then
    puts("Yes")
  else
    puts("No")
  end

end

solve()