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 Fortran (gfortran v4.8.4) (judge verdict: Accepted)

program main
  implicit none
  character(4) S
  integer i,j,ans,x
  !read(*, *) (L(i), i = 1,N)
  read(*, *) S
  ans = 1
  do i = 1,4
    x = 0
    do j = 1,4
      if(S(i:i) == S(j:j)) then
        x = x + 1
      end if
      
    end do
    if(x /= 2) then
      ans = 0
    end if
  end do
        
  if (ans == 0) then
    write(*, *) 'No'
  else
    write(*, *) 'Yes'
  end if
end program main