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 fa
  implicit none
  integer ::i,j
  character(len=4) :: S

  read(*,*) S

  if((S(1:1).eq.S(2:2)).and.(S(3:3).eq.S(4:4)).and.(S(2:2).ne.S(3:3))) then
  write(*,'(a)') 'Yes'
  elseif((S(3:3).eq.S(2:2)).and.(S(3:3).ne.S(4:4)).and.(S(1:1).eq.S(4:4))) then
  write(*,'(a)') 'Yes'
  elseif((S(4:4).eq.S(2:2)).and.(S(3:3).ne.S(4:4)).and.(S(1:1).eq.S(3:3))) then
  write(*,'(a)') 'Yes'
  else
  write(*,'(a)') 'No'
  endif



end program fa