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 aaa
implicit none

integer :: one, two, three, four
integer :: a, b, c
character(4) :: s

read*, s

one=iachar(s(1:1))  + 1000
two=iachar(s(2:2))  + 1000
three=iachar(s(3:3))+ 1000
four=iachar(s(4:4)) + 1000

a=(one-two)+(three-four)
b=(one-three)+(two-four)
c=(one-four)+(two-three)

if(a==0.or.b==0.or.c==0) then
write(*,'(a3)') 'Yes'
else
write(*,'(a2)') 'No'
end if
write(*,*) one, two, three, four
end program