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 main
character*16 :: a
integer :: x,i,j

x=0
read(*,*) a
do i=1,4
do j=1,4
if(a(i:i) == a(j:j)) then
	x = x + 1
end if
end do
end do
write(*,*)x
if (x==8) then
write(*,*) "Yes"
else 
write(*,*) "No"
end if

end program main