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 test
implicit none
character::S*4
read*,S
if('S(1:1)'=='S(2:2)' .and. 'S(3:3)'=='S(4:4)' .and. 'S(1:1)'/='S(3:3)') then 
print*,'Yes'
else if ('S(1:1)'=='S(3:3)' .and. 'S(2:2)'=='S(4:4)' .and. 'S(2:2)'/='S(3:3)') then
print*,'Yes'
else if('S(1:1)'=='S(4:4)' .and. 'S(3:3)'=='S(2:2)' .and. 'S(1:1)'/='S(3:3)') then
print*,'Yes'
else 
print*,'No'
end if
end program test