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: Runtime Error)

program main
  implicit none

  character a,b,c,d

  read(*,*)a,b,c,d
  if ((a == b) .and.(c == d)) then
	write(*,*)"Yes"
  else if ((a == c) .and.(b == d)) then
	write(*,*)"Yes"
  else if ((a == d) .and.(b == c)) then
	write(*,*)"Yes"
  else if ((b == c) .and.(a == d)) then
	write(*,*)"Yes"
  else if ((b == d) .and.(a == c)) then
	write(*,*)"Yes"
  else if ((c == d) .and.(a == b)) then
	write(*,*)"Yes"
  else
	write(*,*)"No"
  end if

end program main