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)

character(4) S
logical check
read*,S

check=.false.
if(S(1:1)==S(2:2))then
  if(S(3:3)==S(4:4).and.S(1:1)/=S(3:3))check=.true.
else if(S(1:1)==S(3:3))then
  if(S(2:2)==S(4:4).and.S(1:1)/=S(2:2))check=.true.
else if(S(1:1)==S(4:4))then
  if(S(2:2)==S(3:3).and.S(1:1)/=S(3:3))check=.true.
endif

print"(A)",merge("Yes"," No",check)

end