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
 read(*,*) s
 if(s(1:1)==s(2:2) .and. s(3:3)==s(4:4) .and. s(2:2)/=s(3:3))then
  write(*,*) 'Yes'
 else if(s(1:1)==s(3:3) .and. s(2:2)==s(4:4) .and. s(2:2)/=s(3:3))then
  write(*,*) 'Yes'
 else if(s(1:1)==s(4:4) .and. s(2:2)==s(3:3) .and. s(2:2)/=s(4:4))then
  write(*,*) 'Yes'
 else
  write(*,*) 'No'
 end if
end program main