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: Wrong Answer)

program abc132a
  implicit none
  character(4) :: s
  integer :: i, m
  logical :: flag=.false.

  read(*,*) s

  if (s(1:1) == s(2:2) .and. s(3:3) == s(4:4)) then
    flag=.True.
  else if (s(1:1) == s(3:3) .and. s(2:2) == s(4:4)) then
    flag=.True.
  else if (s(1:1) == s(4:4) .and. s(2:2) == s(3:3)) then
    flag=.True.
  endif

  if (flag) then
    print *, 'Yes'
  else
    print *, 'No'
  endif

end program abc132a